Because you can't pick what it fires at, and it adores firing at passing seagulls and maxims instead of IS2's.
And it will still kill the seagulls and maxims horribly and then come around again since it loiters and hit your tanks in one pass unless its an is2.
Are you seriously saying this ability wont target tanks over infantry? it targets and murders everything in sight...
please...i've been on the other side of this bs many times and i could have a popcap amount of infantry nearby and itll still wipe my tanks in one pass.