CRT scanline-"like" behavior was intentionally used for color graduation blending. It ultimately depends on the game, but designers were actively using it in their designs. Because that was in essence, what they were seeing.
Pixels werent perfectly square, color bleeding was a thing, so was flicker (line based image reproduction).
There are games out there that look atrocious with full number integer scaling, and need "something" (different scaling filter, blur, or scanlines) to become anything other than a pixelated mess.
Chrono Trigger is one that often gets named, but the concept extends well into the 16 bit aera as well. PSX games like Silent Hill, RE2, or Chrono Cross were designed with the reproduction "imperfections" in mind. If you simply upscale the textures of the time, you arent even getting close to the intended experience.
Even turning on bilinear filtering in those cases is "better" than getting a cleaned up upscaled lowres texture, that never was meant to be seen "upscaled and sharp" on a big screen TV.
edit: Found a good video to illustrate: This is Silent Hill filmed off a Sony PVM (vertically scrolling line is an artifact of refreshrate mismatches between the video camera and the TV and not there in real life):
h**ps://
www.youtube.com/watch?v=RqcDaTY0mNs
This is Silent Hill (uprezed even) on a current version of BeetlePSX (best renderer possible for this game):
h**ps://
www.youtube.com/watch?v=18DuElvRz2I
If you look for immersion and depth of a certain mood, its obvious which one wins. Its not even close.
You also see, that a low poly model, with the reproduction imperfections of the time, can actually look far more "realistic", than its uprezed counterpart today.