I've tried to answer a few since I joined this SE and I personally think that it is not a problem that spams the platform - and the way the community handling is current handling this is just fine.
Imo, there are roughly three categories of questions:
- The person provides enough information and a "motive": These can usually be worked with and there is a chance to research and communicate with the user -> no problem at all, usually good enough for useful comments or answers.
- The person doesn't provide enough information but will eventually respond via comments or edits -> also leads to some kind of answer/resolution. In worst case, these vanish in the archive unanswered but there is some interaction
- A single picture with no context gets thrown in and asking to "ID my bike" and no intention to improve the post -> From my experience, these get downvoted or closed rather quickly
At least now, in 2024 after the Covid cycling boom, there are usually one or two "ID" questions on the main page (out of ~50 shown), so I think this isn't a massive factor, anymore.
On the other side, I agree with Weiwen's answer that this usually doesn't provide any community value, its very unlikely that any of these questions can be used as reference for another, I think I've seen a few examples on real old 30/s40s40/50s bikes but mostly, we have standalone cases.
However, I don't think it impacts the overall user's experience and if you really don't want to see those, you can hide the tag. :)
Conclusion: Not off-topic for me, just stay vigilant when it comes to quality.