A good question and one we frequently get.
The Soul currently comes with latex ankle seals for a few different reasons from a manufacturer’s perspective:
1) Latex socks would be much more fragile and would require a boot over top to protect it anyway - thus why not just go with a regular neoprene surf booty to begin with. It’s the booty that keeps you warm, just having latex between water and your feet will not keep you that warm at all (although admittedly dry).
2) With latex seals and not socks, you have the choice of going barefoot when conditions are warmer but still cool/cold water temperature. For those of us using the suit for SUP, kiteboarding, or other boardsports, we generally prefer the least amount of material between our feet and the board as possible. This gives the best connection to your board.
3) If you are kitesurfing your feet are moving and tactile. With the drysuit and a good pair of booties my feet never get cold whatsoever, despite ridiculously miserable conditions around me. The extra body heat you now have because of wearing a drysuit helps keep your extremities nice and toasty.
We find most folks who insist on having the built in socks/boots are into sports where their feet are not moving. If your feet are wet and not moving, it makes sense to keep them dry, but it takes minimal movement to keep them warm otherwise when wearing a Soul drysuit.
Hopefully that helps!