The following do not seem to be reasonable answers:

They seem like reasonable purposes to me.

It seems that at least in some cases when I ask "Does this thing have a purpose?" the kind of answer I'm looking for includes "someone deliberately created it" but excludes "it's valuable for someone".

To me, the purposes of a thing are all purposes that purposeful agent have for the thing. What purpose does X have for Y? Among those questions, you can always ask "What purpose does the creator of Y have for Y?"

If "Does life have a purpose?" is like this, whether or not other people value my life wouldn't to be relevant to answering it.

It's irrelevant because you have a purpose for your life (presumably), so any additional purposes for your life are superfluous to the question - we've already concluded that your life has a purpose by noting your purpose for it.