Digging weeds and their roots up one by one by hand out of cracks in concrete/asphalt is much slower than spraying. Also much more physically challenging, which is a metric I didn't care about when young and able bodies but nowadays is very relevant to me. I'm not saying roundup is good, but there are plenty of reasons for it to be appealing. I haven't tried the boiling water method yet, it seems like it'd be easier than digging but harder than spraying, unless perhaps one has a mobile, outdoor source of boiling water.

What is the point of removing weeds from those cracks in the first place? Do they cause some kind of physical harm to creatures or objects that move on that concrete or asphalt surface?