Try playing something softly, or at least with your light touch. Turn up the volume, turn up the velocity sensitivity. Play a rocker on the piano, or a funky riff on a Rhodes. Record it.

Now turn down the volume, turn down the velocity sensitivity and curve. Play the same part, and play hard... Record it.

Compare the two. Odds are, they will sound VERY different, rhythmically, emotionally and sonically. Look at the two files in a MIDI sequencer (record them as MIDI first). Look at how different the velocity levels are. Even if you get them both in the same ballpark about average level, the ranges will be totally different.

Now play them to a non-musician. Ask them which version they prefer. 9 out of 10 times, they'll pick the more muscular performance. Rock, funk, and so many other musical styles are all about energy and attitude. You can't tickle your way through them
An arranger is just a tool. What matters is what you build with it..!