The current trend is that many gamblers play games from 3rd party providers although the game is not provably fair. No doubt that in house game with provably fair system has its own market and there are still many gamblers play such game. In this case, casino has their own target and budget. Maybe having games from 3rd party providers is easier than creating their own games as it may cost them some more money to develop the games.
Well, I am not sure about the current trend. But, You are right. Integrating 3rd party games is so easy. And Sometimes a few providers offer free Integration. As I have already said in my previous post, Every game has its different fanbase. 3rd party provider games also have a fanbase. But, I am sure that The fanbase of the In house games is bigger than 3rd party game fanbase. I don't know which games you like most. But, I guess a lot of people agree with me that, In-house games are more popular than 3rd party games. Yeah, Budget also matters. To build an In-House game, You need to do advanced development and it will cost you a lot of money. So, Yeap. The budget also matters.