Sure, it's just a game... but it's also a $60 expense, which I think it's reasonable to expect plays as advertised.
There's way too much nonsense in the current game industry where you pay retail prices for new game releases that are really still only "beta" quality.
Well, No Man's Sky has two issues. First, it's the opposite on pricing - you hear of AAA games priced at indie levels, but NMS is an indie game priced at AAA levels. (And it IS an indie game - the developer's other game was a mobile one). But that is specific to the way Sony marketed it.
The beta thing is huge, and it's because PC ports don't make much money, so everyone concentrates on console first. (Mostly from piracy - the PC market is bigger, but the piracy rate far exceeds the larger market proportion).
And consoles have a long lead time - if you want your game out in December, guess what? It's too late right now to make it - you'll be in for a 1Q 2017 release at the earliest. You need at least 3-4 months lead time between certification (easily a month, maybe more), pressing (just a long queue of other people wanting discs pressed so you schedule yours somewhere in there), packaging, shipping and distribution (you want to get it to the retailers warehouse at least a couple of weeks ahead of time so it can be received and shipped back out and arrive the day before, though if it's a larger shipment, you might want to give them more time).
So that's why there are day 1 patches - after cert, your devs will be idle until the game is released for a few months. They can work on DLC (much shorter cert time), bug fixes, etc.
Of course, this is on a console, so most of the fixes are developmental ones - game flow, etc. Once you release on PC, it's a wild west with multiple types of graphic cards (all of which have their own quirks), processors, etc.