Comment by mgfist

Early investors (the main ones at least) usually get pro-rate rights - which means you can invest in later rounds to maintain your ownership percentage (i.e a later round dilutes your ownership, so you invest a bit until the ownership stays the same).

But the pref stack always favors later investors, partly because that's just the way it's always been, and if you try to change that now no one will take your money, and later investors will not want to invest in a company unless they get the senior liquidity pref.