basically the sophistication required to change lines and markets for savvy punters whilst offering better lines and prices just too much work to justify it for most places, if you think someone is sharp you can just restrict them and that takes a few hours work maximum
It's not as hard as it sounds. You would still have your base prices and then just squeeze/increase the overround as appropriate. Much the same as when people talk about 1to1 CRM experiences, in reality it's just levels of segmentation rather than true personalisation.
It is a bit pointless though as you say, restricting works and is easier. They shouldn't even need much manual intervention for that any more. There are enough data points available to feed a ML algorithm and get pretty accurate predictions on which customers aren't going to deliver a satisfactory ROI over time, and auto flag/restrict them.
The biggest problem (both for sports and casino) is getting that answer quick enough. New customers abusing sign up offers is a massive leak for gambling operators and forces them to enforce all sorts of restrictive terms that end up hurting them twice because the genuine punters get pissed off.