To answer the OP's question: Because it gets me moving.
I like all kinds of music but hard rock/metal tends to be largely what I listen to the most. There is just something about a power chord...i don't know why but it just draws such a strong reaction from me.
And different songs/bands/etc.. have a different effect on me and as such I listen to them when I'm in different moves.
For examples, songs like
[YOUTUBE="E2NyPbT2WoY"]Black Sabbath - Paranoid[/YOUTUBE]
[YOUTUBE="EXHnTKcjTL0"]Judas Priest - Painkiller[/YOUTUBE]
Seriously get my blood pumping and get me moving. I can not sit still with music like that playing.
On the other hand, some rock songs are just good songs to listen around the office like
[YOUTUBE="Cm2-K6ttHYs"]Led Zepplin - Good Times Bad Times[/YOUTUBE]
and other songs are songs that inspire feel good/postive/want-to-chill with my friends music like
[YOUTUBE="csTNcH-7rVs"]America - Ventura Highway[/YOUTUBE]
[YOUTUBE="LEOxMsTxLOE"]The Verve - Rather Be[/YOUTUBE]
I could literally go on but...I'd rather just leave it at that.