Because singing in English means Worlwide success (and Japanese success too) as to singing in Finnish means....mmm European success? I doubt even that.
i don't think that finnish sucks (just listen to turmion kätilöt to bring this band along again ) but some bands just don'T wanna sing in their native language cause they think it doesn't suit their music. and i guess so do bodom
Finnish is indeed quite hard language to write lyrics with. You can make things sounds cooler in english alot easier. Also it's gonna be extremely hard to get any gigs abroad when none can understand a word you're saying. If you want a band with good finnish lyrics try out Moonsorrow, specially Verisäkeet. The older ones can be a little cheesy but songs like Karhunkynsi and Pimeä are really well written.