Mostly never. People are using to many apps today and they don't have time to read every TOS. I'm not talking just about gambling. I personally use more than 20 apps on my phone. And betting sites have mostly similar TOs so I just assume everything will be fine and just click accept.
Adding to it, most of the times Terms of Service are long and use quite complicated language.
Some TOS takes more than 20 minutes to read.
usually the Lindy effect and honest user reviews are better to knowing if you can trust the online casino, since they could disrespect their own TOS if it's a shady website.