Poor hyphenation for runts?

Recently, while writing a document, I noticed that groff hyphenated the last
word of the last line of a paragraph. This looked very ugly, so I inserted a
\% before the word to prevent it, but that made me realize this left a runt at
the end of the paragraph. I was wondering: is this intentional by the
hyphenation algorithm? Does it do this to avoid runts? Because I think leaving
half of a word on the last line is worse than leaving an entire word on the last
line :p (personally, I don't even find runts that bothersome... maybe I'm a bad
typographer...)
-- 
S.