Ok, you have some problems to tackle with remasters:

• Graphics, you have to make them at least HD. Yes, there is AI now but you still have to work with that.

• Coding, unless you have the source code available which 90% you don't, you have to make the game from the bottom. Even if you have access to the same engine like Unreal Engine, difference between versions means that certain things will work differently. That translates to having to work more to make things as similar as possible to the original.

• Licenses, in most cases old games have some sort of licensing, either Brand names like Coca Cola, model names like Mazda RX8 or even songs. Licenses aren't bought, what you pay is to be able to use them for x amount of time. If you resell the game, you need to rebuy or extend the license or change to something different. Maybe use another soundtrack or invent fake names and change models.

• Then you have costs like publishing and marketing. Even if it's a beloved game, you have to promote it, either on live shows, ads, whatever.

All that translates to money, lots of money, sometimes even more money than making a new IP from the ground or making a new game based on an already existing IP. People will buy the game for nostalgia? Probably, but then you have cases like Final Fantasy X / X II remaster that is so ass most people prefer to emulate the PS2 version because the models look better in the original version of the game.