Because I always wanted to pay $10 for a 1 hour sword/gun model that was slapped on template animation set. Good goy, buy dem hats. That's almost the same principle as 7 days to die $500,000 "upgrade" aspect, where if they get another $100,000 they'll add one new feature or some bullshit like that.
You didn't presented me any specific case of the micro trasactions therefore I was talking about all such games in general. The case you're proposing here is obviously something that I wouldn't agree since it's pretty obvious how ridiculous it would be for some developers to be this greedy.
What I'm trying to say is that there is nothing wrong with microtransactions as long as they aren't gamebreaking by giving the buyers enormous advantage in terms of gameplay or are ridiculously over priced.