The biggest Pro of course is stability! You don't have to wonder as to whether or not your deposit is secure, who exactly has it etc, and when you want to get paid, you don't have to jump through any hoops which we all know comes with the offshore landscape far too often or incur mysterious delays. Also, it's extremely easy to move money around locally compared to offshore. Can you find better bonuses online sure but they often (not always) come with some of the headaches mentioned above.
The cons for some are more than others as to exposure tax wise etc. As to being limited more locally than offshore, I am not sure the gap is all that big for most players but it may be for some.
Now that Louisiana has legalized and sportsbooks are open with apps about to launch would I still play offshore? Probably at least for a little longer but it will be significantly less for sure.
Line shopping is def important but here there are already several options to get funded including BetMGM/Ceasars/Fandeul/Draftkings/ and a couple of others, so using offshore to line shop isn't as necessary.