People who are used to the land based casinos might end up spending time in the physical casinos. The online version might not give them the experience they get from the land based ones. Somehow the gamblers will feel lazy and starts spending time sitting infront of the PC or some other devices for their gambling needs. When it is land based casinos the money is not just out of gambling, more business happens around and the gambling House doesn't want to limit it. In recent years during the COVID lockdown more land based casinos had their online version, but those were stopped once after the services resumed.
Well, I don't think this stops them from running an online version of their casino if they really want to, the more reason I think land based casinos are not really interested in having an online version is simply because of contentment, building, operating and maintaining an online casino comes with great responsibility and expenses, you will have to pay software engineers, security experts, data analyzers, programmers, hosting services and so on, you will still have to hire and pay customers service personnels, and on top of all this expenses, you will have to spend millions on marketing and still worry about gaining customers, and also consider that there is a lot of competition amongst online gambling casinos already.
If you combine all this ive mentioned and many other i forgot to mention, you will discover that operating a land based casino is way easier than operating the online version, and when some of those guys who own a land based casinos consider all the facts, they are like "i am already earning enough more from the based casino, why the stress of trying to open an online version, that money could be invested in another business entirely outside a gambling casino".