There's a control/speed tradeoff. The slower you play the more you can do with a note, bend, vibrate, harmonics, volume swell, whatever. Play fast and you loose all that. On the other hand melodic lines must be shorter than our attentions spans. This requires that intricate many-note lines may need speed to resolve properly. Having a range of different speeds adds interest, my fave guitarist is probably Satriani, he can sweep,tap, legato like a monster but his slow play is also brilliantly expressive.
If I couldn't laugh at myself how could I laugh at someone less ridiculous?