I think another reason we have “styles” is that people in different areas of the world work with whats available to them and try to play to their strengths. The soft water in Pilsen, the (lack of) availability of hops and malts in Scotland, the mineralized water in Burton, etc.
Then styles develop due to changing times, regulations, and/or tastes. For example all beers were brown at some point before malt could be dried cleaner, leading to pale beers and a fascination with clear glassware.
British beers became lower in gravity due to taxation. Brewers in the UK did not intentionally set out and plan to brew 3.5% and 4% highly hopped beers. In fact UK brewers brewed many strong beers, how many follow Ron Pattinson?
American beers got lighter during WW II when more men were at war and breweries were catering to the tastes of women.
Nobody was brewing milkshake IPAs 50 years ago. Thats a sign of the times - people have abundant time on their hands and alot of resources including newly developed hops to try something new.
I don’t think these things were planned. They are adaptations. I don’t see styles as set in stone, harshly defined things. Styles evolve over time to be a combination of what brewers can produce and what people at any time want to drink. Breweries wouldn’t make NEIPA if nobody was buying it. British breweries would brew more Mild if more people were buying it.
Style is just an attempt to describe what somebody is or was making somewhere in the world at some point in time.