Because it's a legitimate concern about the industry. You're kidding yourself if you think there's literally 'no' cost. It crowds out releases and dev resources, even if to a lesser extent then most other releases. People don't like this. It also sets a precedent in the industy that putting little effort in can justify a high price tag, which is also a problem. You may not be concerned, but others are.
Just because some of these people don't like it doesn't mean they should be allowed to derail threads.
Even when the remaster is confirmed to be great, these people will still bitch about it like everything is supposed to be about them, completely disregarding the many other people that could be and are interested. No one else cares that you completed the game last gen. How does that concern those who haven't?
Get over yourselves and stop acting like it's buy or die. It's an option, just like PS2 remasters on PS3. Don't want it? Ok. Move along. Thread derailing for this is just as bad if not worse as port begging.
If I want to play these games remastered on my PS4 because I no longer have (or never had) a PS3, for example, who's to say these remasters shouldn't exist?
"But people don't like it." Holy shit, and? Buy something else. Nothing else to buy, you say? Go read a book. Do something else.