Why are there mathematicians that do not use computers?

Why are there mathematicians that do not use computers?

I was watching a video on Andrew Wiles and his proof of Fermat's Last
Theorem and I quite liked the video, especially the complexity of the
proof only to prove a simple concept which can be understood by most
people. I also liked the graphics they used to illustrate elliptic curves
and modular forms.
But then Andrew Wiles said that he never uses a computer, he only uses pen
and paper and I also heard of other mathematicians that don't use
computers.
Do they not use computers because there are problems only a mathematicians
can solve or are there other motives? Wouldn't the proof have taken much
less than 7+ years if he used a computer?