Do you use other people's razors?

So I ask this because I have a cousin who's been using used razors that don't belong to her for years. A while back, she'd use our uncles razor, thinking no one would ever notice, but we all found out at some point. Recently, she came to stay at my house for a few days and I noticed my razor's been moved and used. I find this kind of thing disgusting and question why she does this in the first place instead of getting one of her own. Is this not such an abnormal thing? Do other people actually do this?
Do you use other people's razors?
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