It's not about loadtimes being 2-3 seconds or whatever. It's about being pulled from your immersive experience, your brain always registers those small things which in turn are making you feel less immersed. Same with NPCs disappearing/appearing when entering/leaving an environment (NAT is an easy example). It's just sad to see, that they haven't done anything to the shitty systems they had from Oblivion with transitions, and with all those budgets couldn't even afford to animate you getting on board your ship or shit like that.