If something sounds better without strict quantisation then....... Don't quantise it. Not quantising isn't a criminal offence, nor will the Gods of MIDI be offended. :-)

Humans are very sensitive to rhythm. We detect slight changes and non-perfect alignments very easily, and those "errors" are what actually gives much music its life.

For example, consider a basic 1950s style rock'n'roll song. The drummer can alter the 'feel' of the entire song simply by playing the hi-hat very slightly ahead of "correct" placing. By 'very slightly' I mean a few milliseconds. The result is a driving backbeat that seems to propel the song along, giving it a feel of impetus and building energy.

Now consider a fairly slow, gentle small band trad jazz track. There the drummer might delay the hats (or ride cymbal) very slightly. This time the track takes on that relaxed, 'late night' laid back feel.

In both cases if strict quantisation was applied the track would lose its 'feel' and be weaker for it.

This isn't restricted to just drums, and sometimes the song is 'pushed' and 'pulled' at different times. An easily found example (try youtube) is Patti Smith's "Because The Night". There are two sections to each verse and a chorus, and the piano and drums work a little behind, on and a little ahead of the beats to give each section a different feel. Strict quantising would destroy that careful playing.

Even electronica isn't always strictly quantised. Shifting notes backwards and forwards a few milliseconds to create a particular feel is quite common, sometimes by shifting the MIDI/audio, sometimes by using a synth's attack envelope. Sonar's step sequencer even allows you to do this per row and the piano roll editor per note.