My thought process is optimization for all the guests. Doing some simple math: Cost of holding wedding at location X + cost of wedding attendents travel + cost of lodging at location X vs the same costs at location Y.

Not surprising, the location where the majority of the attendents reside is usually the most economical for the total cost the wedding for all involved. I do understand that it is the couples wedding and they can choose where they want to hold it. I am surprised that more couples (in my limited experience) do not consider their guests expenses more.