I'm curious what kind of weld you were expecting on that weight !!!

A balance needs a specific weight - which they pick from a selection of weights. The spot weld adds no additional weight so they spot it on and they're done. If they stick welded it on then they'd have to spin it again and take weight off because the stick adds weight. Furthermore, its a cast iron drum and there are very few methods of welding cast iron. Any drum I've ever seen had the weights spot welded on.