Well I think it's more about the market. Let's take Square as an example. They've lost many in the process of making that first Final fantasy movie. And I also heard that games like "Chrono Cross" didn't sell good in Japan (Although it broke the expected records in USA) . The problem is that most fans like "Final Fantasy" Although Square have more good series (Like Parasite Eve) but they don't sell the same way. So what should Square release between each "Final Fantasy" game and another? A remake, or a port or even some less quality games with the name of "Final fantasy" on (I'm talking about Final fantasy tactics advance which had a less than average storyline).
If you check Square-Enix's site you can find a category that's called "Popular games", which contains only three series : "Final Fantasy", "Kingdom Hearts" and "Fullmetal Alchemist".
So what would make Square release now a risked probability game unless it was very well planned even with less number of copies. Instead they can keep milking FF7 and add more and more titles with it's name (Are they 4 titles so far?).
Side note : Do you know that Square rereleased FF1 4 times after the original NES game? Wonderswan, PSX, Japanese mobiles and GBA. Oh great and still ppl buy it. Do you still think companies should stop remaking and porting?