...because I've been playing as them since the old Heroes 2 and have never regretted it... the fourth installment was a bit disappointing, but that's okay... I played it, I'm playing it, and I will continue to play it, and no matter how much they criticize the Fortress for being expensive or having weak units, it's the best (they just don't know how to use it)... and a swarm of Kshatriya Rakshasa with a Talisman of Luck + Battle Fury + Initiative or + Magic Resistance will crush everyone and tear anyone apart, no matter what they say or how much they boast... :)

...by the way, when I switch to other factions after playing Fortress, it's not interesting; it's too easy to play... ;) IMHO.