I know nowadays that doesn’t matter as much due to most DVD players or disc drives being region free, but I recall the time when I was younger in the late 90’s to early 2000’s most discs were region locked based on where you bought a copy (basically the same as buying a Japanese N64 cartridge versus an US one) meaning they won’t work when in another country.
For instance: I’ve purchased the first 2 home alone movies in Japan during my trip back then when they’re re-released on DVD (encoded as NTSC) while I come from a country where most discs by default are PAL so they didn’t work on my normal DVD player, having to purchase a multi region DVD player just to watch them. (This was before streaming sites).
Money and sales charts
Being top of a sales chart was a big deal a couple of decades ago as it usually meant a product got better placement on the shop shelves
So then marketing budgets could be focused on different areas at different times, meaning greater chance of getting higher in the charts
That and localisations generally taking time and studios not wanting to cannibalise sales of a local version with imports
Also regional pricing, they could sell more in poorer countries for lower prices, but they didn’t want to give up the greater amount they can ask for from richer countries
Edit: clarity