Another MMORPG question

In general, how important is “crafting”? Does it vary from MMORPG to MMORPG? I read a bunch of web comics and blogs, and some of them are MMORPGers, and they talk about stuff like “I worked on my knitting craft last night and managed to finish this lovely sweater” (ok, that’s not quite right – it’s usually gloves or boots or something). But to me, the only thing more boring than actually knitting or fishing would be to sit in front of a computer watching a simulated “me” knitting or fishing.

If I decide to spend all my on-line time questing instead of doing boring crafting stuff, will I find myself unable to reach higher levels or to afford decent arms or otherwise held back?