Because the architecture behind a network is far more intensive than setting up P2P servers. When you play a game online on PS4, you're playing it on PSN, not the server list that varies wildly from dev to dev. While netcode isn't created equal, you know the product will work.
To summarize all the work that has gone into it as the same thing as digital storefronts or to deny the leaps and bounds in product quality.... Man, I don't even know what to call that. Blissful ignorance? It's like how people falsely say that PSN/XBL are doing the same thing as Steam when Steam hosts absolutely nothing off store. They don't offer the same product at all.
If you don't think the value is worth the cost, then don't buy it. I will pay for it because I place very high value on cloud saves, PSN discounts, and free games.
You know, we are on an online forum with the ability to reply to people ... you could just ask for clarification instead of calling others ignorant instantly. I will admit I worded that badly as there is a common misconception that Steam and PSN are the exact same, so I can see why you assumed I was being ignorant ... however that's not what I was getting at and you could just simply ask me for clarification before hammering down judgment. Just to be clear, I *know* that PSN and Steam are different, PSN is much more complex and hosts multiple games. However, even if PSN has higher costs because it's an entire network and not just a system of servers spread around one individual product ... that doesn't really change the fact that you're paying money for a console for the purpose of playing those consoles games, no? That's kind of the point of the consoles, and in 2018 you'd expect that the ability to use internet freely comes in that package.
Simply put, PSN's problem isn't the value, it's the fact that you have to pay to use online in the first place. Your excuse and Sony's excuse is the value, but that value could just be put behind any other subscription service. So they have to lock the value behind the ability to play online. Most people who have PSN are paying for it JUST BECAUSE you have to use it to play online. You can use the excuse all you want of the "value" but I would rather just play online for free and have the option for a separate subscription service ...