Just my opinion, but almost all regional aircraft I see are always taxiing at quite a sporty pace. Now, before you all jump on me...
** HERE IS MY DISCLAIMER!!!*** I do realize I work for AA and we specialize in safe taxiing..
... however, if you watch regional-size aircraft and compare them with bigger aircraft, the smaller ones tend to taxi a lot faster. Must have something to do with the multi leg days and wanting to get them over with. When I was at ACA and we had 7 leg days, we taxiied a lot faster than I liked just because we wanted to wrap it up.
It's also easier to maneuver a smaller aircraft than a large one... and don't forget about perspective - when you're sitting a lot lower to the ground, going slow feels REAL slow.
A notable exception to this rule is obviously SWA... and, well, their contract speaks for themselves. They aren't paid by the hour like the rest of us - and they are all part of a winning team, again unlike the rest of us.
But as a general rule - the regional guys taxi faster than the rest. It's just the way it is.
Funny side note - one time we had just landed at DFW and were northbound on Kilo... an ATR was beside us on Lima and just blew us away, we were doing a respectable (and shocking for AA!) 15kts... the CA and I were like, holy cow, can you say future SWA pilots? then DFW Ground got on the horn and told them, "Eagle XXXX, please respect AIM-suggested taxi speeds.." priceless!