IHT or Bren Carriers (mario karts) get totally quite expensive when fully loaded. So two BC with Piats is alot of MP and if the opponent is for example a PIV it ain´t hard to kite the karts + especially Piats can´t hit anything that is moving.
If the P IV stand still and turn the tank in the mario karts direction the kart will get pwnd. But has to be in open.
Not everyone has a P4 on the field or anykind of tank really when the Clown Car role around. Most people always start with some sort of AT (Pak/ATG) and you shouldn't av to rely on a tank to do a job of a AT gun. Also no-one seds only one clown car in against anyunit. They always throw 3-4 of them in. 3-4 clown cars with hand held AT will beat any tank/support weapon/inf hands down.
It might be expensive to put PIATS or anykind of hand held AT into a clown car but the fact is that the brens/IHT or anykind of vehicle tranport is too strong against AT and getting spammed like hell.
This is the main problem with clown cars at the moment. They are too strong and take many hits from AT and don't die. They r too available so people buy like 6 and spam them too hell. When you finally destroy the clown cars the units inside don't take any damage at all, jus continue to kill all ur stuff until you bring up an another MG and mortar to finish them off cos your other support weapon got pwnd by the clown car spam.