Before battle you carry everything you will wear into battle + a tent, some food, etc.(Nobles had packhorses, and in some campaigns soldiers too, but htis was not majority) In battle you carry much less than in prebattle. Weight in battle is rarely a concern.
Halberdiers didn't use many shields because guns had become common when halberdiers became common. Shields can stop crude guns, but aren't reliable enough to manufacture.
A small shield attached to the wrist while you are wielding a two-hander barely hinders your attacks in at all, the only downpart is that it throws your swing off-balance, but the same can be said of heavy shoulderpads, and no-one says heavy shoulderpads shouldn't be equipped with a two-hander. The shoulderpads are mostly aesthetic, and I thin they are ok even though they are illogical. But why do people dislike 2h weapons and shields?