The relevance of engine displacement

[AmericanThunder]

Has anyone ever noticed how even different manufacturers come up with engines of the same size?
It's rare one breaks the mold and announces something different.
So for example, Ford, Chevy and Pontiac had 400ci (6.6l).
Chevy, Pontiac & Dodge had 350ci (5,7l)
Both Chevy & Dodge have settled on 6.2 for their supercharged engines.
And in the UK, 1.6, 1.8, 2.0 and 2.8 are common from most manufacturers.
So why?
I'm sure the answer is bore vs Stroke and square vs under/over square along with configuration and packaging constraints. But perhaps there is more too it? Why did/do so many manufacturers lineups feature a 5.7 or 1.6 offering? Or perhaps they have done in the past - I can think of many engine sizes from bygone years that no longer feature today.
Thoughts?

 

[TransAmDan]

Mustangs seem to have smaller engines, like 5.0l, or do they have a 4.2l?
I guess there is an optimum bore vs stroke. But there are soo many different sizes, although probably less now than before. A lot of manufacturers using the same engine even in every day cars. Like an Alfa using the same engine as a Vauxhall Vectra. I guess that helps with parts supply standardising on the same platform.

 

[AmericanThunder]

Yes , optimum bore vs stroke is the square configuration I referred too.
You are quite right, I had ignored the common platforms shared by lots of manufacturers and perhaps they even share some R & D?