Default ram setings are not enought to suply minecraft.
Chunk loading without changing java arguments is nearly 700% slower than alocating it with 8gigs of ram. With default seting i had to wait for years for chunks to load, by changing them chunk loading is almost instant.
opinions:
I think mojang needs to work to lower ram usage. It eats more than chrome. If imposible to make dynamic memory alocation, atleast inform players that those task require more memory.