At 3km+ out, no Panzerfaust or AT4 can hit the tank. Only a guided Javelin, but those are heavy (heavy for an infantry to carry at least) and expensive.

But yes, the whole plan of today's combat is combined arms. Tanks doing what tanks do best: long range sniping and sometimes taking advantage of armor to say... get rid of anti-personel land-mines and other lesser explosives.