These questions fall into two categories:
- Questions that specify the actually used version in the question body ("I am using Magento 1.9")
- General questions that are looking for answers valid for all common Magento 1 versions.
How should we deal with those tags?
I find (2) a valid reason as long as the existing magento-1 tag is still discouraged (See Does magento-1 tag make any sense?). Not adding a version tag at all will soon be a problem with increasing number of Magento 2 questions.
In case of (1) it looks like an attempt to gain more visibility by tag spamming. Since the maximum number of tags per question is 5, I don't know if it really has impact in this sense, but it devalues the meaning of these tags.