You dont need the main gun to engage a truck or crunchies.
Yes,
Something a lot of us in Korea felt we needed when the M1A1 replaced the M1 there in '95. Forty 120mm vs fifty-five 105mm. Big difference. Why waste a HEAT round on something the M2 could take out. Army finally got something called the CSSAMS (Acronym might be spelled wrong) around 2004. Every once in a while a picture will show up with one mounted.