People eating and drinking on the go

I often see people drinking coffee and eating while out and about and cannot understand the need to do this. Can anyone enlighten me?
It’s not people rushing around on lunch breaks but people in general you see them in town visiting shops hot drinks in hand food being eaten on the go. I hate it in the clothes shops as it spoils my browsing when someone next to me has a hot drink and we are stood shoulder to shoulder looking at the same clothes rail. I tend to walk away as it unnerves me. I would much rather sit down and enjoy the food and drink and do wonder why it is the norm to do this.