I think there is a reason for that⦠Simply because general crafter thrall hunting is way more difficult on Siptah, there are way less of small camps especially on the main island which is barren compared to the southpart which was added during early access.
To better understand why the main island of Siptah feels barren perhaps is because at early access launch there were no human camps on Siptah, the southern parts didnāt even exist, so thralls could be gotten through 2 kinds of surges, done by the Leyshrines or wild surges which activated themselves randomly but in set spots out of many possible.
The wild surges could be from many different factions, but they were limited to T1-3 fighters, archers and crafters, I kinda miss those wild surges, they were actually a bit fun when thinking back, and also gave low level players a chance to get some decent thralls early on 
Anyways as I said Siptah was initially without human camps and players felt it was too empty so the devs added some human camps, but since players may have built in the areas they wanted to place them, they then warned us with a map showing where they would place so that players could move from the area before they released the 2.3 update 
As you can see that is not a whole lot of camps and also widely spread out compared to how close camps are in Exiled Lands, also many of the camps had/have way lower chance of spawning higher tier crafters, I think it Was Firesparks81 who did a check on these camps (not sure it was him), but again Funcom wanted the main mechanic for getting good thralls to be the Leyshrine surges, and at the same time they removed the wild surges which actually lowered the chance for low level players to get a decent T3 thrall.
And a little later(2.4) they added the 3 biomes south of Siptah main island, which did add a decent amount of camps with a possibility to get some T3-4 thralls, but it is not low level friendly place for most players, it is far more dangerous than most of the Exiled Lands map.
Start a fresh game in both Siptah and Exiled Lands and see how fast you can get decent thralls especially at least T3 blacksmith(needed for crafting steel cheaply), T3 Alchemist(needed for easy oil production) or any other at least T3 worker thrall, my bet is that you would have all you need in Exiled Lands long before you have it on Siptah, even if you count out Sepermeru and Sinnerās Refuge, pretty much any type of T3-4 worker thrall can spawn in most exile and dafari camps, that is not the case on Siptah, some of the Siptah exile camps donāt even have a crafter spawn and most that do is limited to T1-2 at best.
On Siptah your best bet is pirates mentioned by @Teng, but even those camps have a fairly low spawn chance for high tier crafters, they also donāt have many of them, but they do have a bunch of archers and often high up shooting down at you, and after the Age of War update beginnings are way more rough, these guys can kill you very fast without much levelling or good armor - It is not that I donāt like a good challenge, I do, but Siptah just feels⦠too much RNG, still like to play there once in a while though just for variety 
You are absolutely right, except for a certain type of brutal Elder purge, I have never gotten anything else than accursed purges on Siptah which did provide me with lots of T4 fighters, but like you literally zero crafters 
Personally I donāt mind Siptah not having maprooms and obelisks, I actually liked that part of it, however for quick access between a thrall outpost and main base I just used battlestandard to kill myself and respawn with full inventory at main base or the other way 
Yes you can absolutely do surges to get thralls and a T4 surge usually spawn a decent amount of T4 crafters.
Surges has and always will bring out the worst in some fellow players, there is a lot of stealing, I remember once doing a surge alone, pretty much all that I knocked out got stolen + a lot got killed by jerks.
However my main reason for not liking the surge system is that it is kind of ordering an unspecified but good quality pizza⦠Yeah bad comparison, I know, but it was the best I could come up with 
I have always like the hunt for thralls and occasionally running into a T4 crafter at the many small camps in Exiled Lands which are so plentiful that there almost was one for every hundred meters unlike on Siptah.
I especially loved the T4 crafter hunt way back when their name meant they had a speciality that only a few others could do, anyone remember how hard Grrr Legbiter was to find? 
when we had character transfer, I had 2 accounts when playing solo, a spare account that did nothing but travel back and forth, guess what the most requested trading object was?
On Siptah the most requested trading objects was RHTS, T4 crafters, stacks of Grandmaster weapon and armorsmith fittings.
In Exiled Lands the most requested trading objects was Eldarium bars, tools, weapons and armor.
Damn⦠I miss being able to transfer, there was so much fun trading back then⦠Oh well Funcom gives, and Funcom takes away, that is sadly just how it is 
I feel like I am going in circles between how things was and is now, better stop here before I start sounding like a broken record, if not already 