Advised against in the late 90s since it was a pretty common habit from the dawn of computing through till the early 90s, and they’d finally realised it wasn’t the best of ideas, even if it was very very fast.
The number of times that Windows has been pwn3d by ‘legacy’ formats - images, font files, crazy stuff - that it’s attempted to parse for thumbnails is pretty crazy. There’s a lot of programmers writing unsafe code out there.