The reason is that Sony wants more data. There's no technical reason for it, as the game has already worked fine without it for months. This is just Sony clamping down on a promise they quietly made and that most people forgot about.

As for the extra hoops, if you're still wanting to play the game and don't already have a PSN account, you'll need to make a free one and link it. It shouldn't require any additional logins after the initial link, so after the initial account setup there shouldn't be any additional change to the process of logging in and playing.

The reason is that sony is the publisher for the game

I read that Sony is doing it for security reasons for safety/grieving and that the game did originally require a PSN login at launch, but stopped it at launch. But I am guessing this is just them saying hey we have this many people using PSN accounts. No other reason to have Steam prompt for login for anything besides the Steam account

The account link was optional, but somewhere they have written that the PSN account will be required at a later stage, seemingly due to issues at launch. Now, people who are living in a country where PSN is not available (which are quite a lot actually) will no longer be able to play, neither to refund, since the launch is months ago.

So it's way more than just having yet another account, which is especially ridiculous in the case of PSN for Steam PC games.

It works just fine without it, so the reason playstation are enforcing has nothing to do with making the game better and something to do with data collection and them profiting from it.

It's a fucking idiot move, burning goodwill for probably very little actual gain

It's a case of the straw that broke the camel's back I think. People are getting sick and tired of needing an account for everything. And this is getting more attention than it otherwise would have both because of how popular the game is and the fact that the requirement is coming after launch. I'm tired of making an account for epic games, for battlenet, for microsoft, for gog, for capcom, for PlayStation Network. Especially when the game has clearly been functioning perfectly fine without it this entire time

I think that people are finally just reaching the breaking point on this and helldivers was just in the unfortunate position of being the one that finally broke that back

but it's not a game dev. It's the publisher wanting to boost active user numbers for shareholder purposes, Arrowhead doesn't gain anything from this happening.