Its called world-building & character development

John's legendary caliber as ferocious, devil-incarnate hitman was still in minds of everyone....even after he retired.

Even then, a spoilt brat killed his dog, took his car & bashed John like dude was nobody. It was only after his Dad revaled who John was, his hitman status dat we ourselves learnt what John's capable off

In Chapter 2, John was reluctant to return. Despite the marker. Add the fact he's gonna kill some higher authority figure that'll incur wrath of High Tables who'll come after his life

Point is. John's mission was only to take-out 1 tycoon lady. It was supposed to be sneak-kill-leave. Turns out he had to fight off Cassian & his men, countless Antonio's henchmen & finally dude was declared excomunicado, leaving his life open to be taken by anyone who wants 14 million bounty...making him open to international hitman (friends, foes all alike)

But even as Winston told John abt all these....John was cool af saying "Winston...tell them...tell them all....whoever comes....whoever it is...I'll kill them...I'll kill them all..." giving frickin tough & cold mfker expression

The way I see it, John was already wounded by several gun shots & tired from all those fights. Dude 1st needs a place for refuge, heal his wounds &  revitalize his body to 100% b4 fighting his way outta entire world. Dats what the scene tries to portray with him running for his life imo