I think this is a pretty legitimate want/need. Let’s say you’ve purchased something from, say, a sex toy shop. If you’re showing Monzo to a friend or something (which, of course, we do all the time), I can imagine you might not want the risk that they see the transaction.
Or perhaps you’ve gone to a gay bar but you’re not out. And you don’t want the (potentially very significant) risk of that being seen by a parent or whatever.
I do think the posts in this thread are tending more towards telling the OP that they’re wrong for wanting this, rather than perhaps considering why it might be useful.