Your friend knows his self and his self control when it comes to gambling so maybe that's also the reason why he'd rather stay on the online casino that he knows than trying out the new ones. It's also understandable that it could get you to spend more on gambling.
As for me, I'm open to trying out other websites that I haven't explored yet especially if I've been hearing good reviews from other gamblers. But if it's a new online casino, I feel like I'd be reluctant to try it out... But since I'm currently trying to limit my spendings in gambling, I am not into exploring other casinos right now. But if I do have extra money I can spend on gambling, it would also be fun to explore other website. Understanding their UI and stuff won't be a problem since that's part of exploring.
If you are open to accepting a new casino, you should be able to make sure that the casino is the one you are looking for and that you have checked the terms and conditions because they will be different from other casinos. Don't regret it later when you find out that the casino is a scam casino that will make you lose all your money. I will continue to use the old casino because I think looking for a new casino will take time and won't be easy. After all, we have to be able to find more information about the casino. And I also don't want to use more money to gamble because that could make me lose a lot of money later.