Not a problem, thus why we have this section, bt dont expect all to be answered in one goal.
In simplest form, from a user position, lets say l want to find an answer quickly for something or a quick question, l can jus go straight to the subdomain without going thru the main one even though they can be on one server.
The other thing is about delegation of duty or authority. Lets say you have a company with offices in different regions or towns of Zim, each with its on admin and contacts, you can then give each admin control of the town domain.
For example, if techzim have in most towns, for Bulawayo it can hav bulawayo.techzim.co.zw. So users there can contact and post using there own language without affecting the main domain which can retain use of english.
If our internet was fast and reliable, with no electrical cuts, then local hosting is the way to go.