Struggle Bug is a bad move for singes. In doubles/triples it can hit and debuff multiple enemies. The move isn't intended for the singles battle format.
This is a very good point. I get annoyed by the useless TMs too, but a whole lot of them that seem useless might actually be very useful in certain situations outside of single battles. In fact many of them are only useful in doubles/triples.
That being said, there are still some that are almost utterly useless.
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