English speakers have traditionally turned to our tongue's Germanic side when we seek to be direct. (Some Germanic words: run, eat, beat, and yes, suck.) But we turn to our French romance roots when we're looking for a little more formality. (Romance words: saunter, devour, chastise.) It's not precisely the same thing, but a similar duality has come to affect our sentence constructions. We get short and direct when we're being casual, but we tend to add layers and buffers when we're reaching for a formal air. Perhaps the X sucks/stinks/rocks/rules formulation is just so blunt it strikes us as unseemly.
Personally, I wish sucks could escape from its slangy ghetto. It's a terrifically punchy little syllable, with that "k" lending it the proven Starbucks/Nike/Kinko's power of the "sticky consonant." And take heart, sucks-haters. Soon enough, another bit of slang will come along and gain entrance into our common language, and it will be vastly more offensive than sucks ever was.
For proof that this escalating battle of raunch has been going on for years, I present a fantastic exchange (click here to listen to part of it) from the 1940 film classic The Philadelphia Story. Witness a mother and daughter debating the relative merits of vulgar intransitive verbs:
Dinah Lord: "This stinks."
Margaret Lord: "Don't say stinks, darling. If absolutely necessary, smells. But only if absolutely necessary."