[westernpopular]

Because non-tech people don't think about which search engine they're using. Doesn't mean it's not bad.

[TheRealPomax]

People care when things are bad. They don't care when things are fine. Not good or great, but fine. It gets normal folks the information they were looking for the vast majority of the time. Whether the results "got worse" is irrelevant when the results are still what people were looking for.

[eitland]

Many continued to use Altavista or something until a friendly sysadmin or another early user showed them Google.

Same with IE, if no one showed them Firefox they just stuck with IE.