It's mainly that way because due to crossing at most places being legal you don't need specially marked crossing and special marked crossings are mostly reserved for special situations.
Like legally speaking there is no direct rule weather a car has to slow down or stop when someone is crossing the road. But if not doing so would endanger anyone the car has to do it anyway. And not doing so means you are pretty much fully liable for any damages this causes (assuming they had time to react etc.). Similar going on a street in a way which forces a car to strongly break isn't legal, as abrupt breaking comes with all kinds of dangers. For many situations especially small streets, low to mid traffic situations or situations with such high traffic that they jam this works perfectly fine without needing any "official" pedestrian crossings anywhere.
There still can be "unofficial" crossing, but they mainly exist to make space at the side of the street i.e. prevent parking cars blocking pedestrians from crossing. This matters especially for people with buggies, baggage or e.g. walkers. It also helps with visibility as small people like children are easy to overlook between parking cars. But they have no special legal handling and aren't loop holes or anything either. Just the normal way pedestrian crossing had been handled in most places before care traffic became big.
Through because "people aren't always careful", "crossing streets with multiple lanes is always a bit scary" and "sometimes traffic is just too high" and similar we have pedestrian crossings with traffic lights on nearly all road crossings involving multi lane streets or streets with 50km/h speed limit. Sometimes there are also traffic lights for things which are only pedestrian crossings, normally with a button you have to press for them to signal cars to stop.
Lastly there are properly marked pedestrian crossings (zebra strips, with appropriate sign) which are special in that cars have to stop if it looks like a pedestrian _maybe_ wants to cross the street. Not just if it would be dangerous to not do so. They are basically a cheaper version of a on demand traffic lights in situations where crossing the street without one can be hard to do safely while there is very little pedestrian traffic at the same time (e.g. on a street where for a long strap is no crossing with traffic lights but sometimes people have to cross in the middle but only a few times a day). Sometimes also used in situations where theoretically not specially handling is needed but due to idk. there being a primary school nearby it's done to add a bit of additional safety.