i think they should make a way to legally add extra games to the systems. 20 games is cool and all but what happens when we finish them all? I think it could be awesome to purchase more games for them
I agree, but then you have to start adding things like wifi/ethernet as well as coding settings screens and wizards to help people set and change their network settings. You would also need some sort of account system (PSN, Nintendo account, etc) as well as screens to set and change settings for that as well - not to mention coding your actual storefront interface, the ability to make purchases, store payment information, etc. On top of all that, you've now got to build interface elements that give users the ability to delete games they've already purchased and manage the system's memory.
These things all seem trivial, but they all involve a pretty huge investment of UI designers, programmers, QA testers, and project managers. Those are soft costs tacked on to the cost of including additional hardware (ethernet ports, wifi adapters, licensing costs for those) which also drives up the cost-per-unit to produce. In business, when the cost goes up the price goes up usually by a factor of 1:2. So if these things all together add up to being, say, $25 per unit produced (just guessing, it'd probably be much
much higher considering the low number of units produced) then the MSRP on the Playstation Classic rises to $149.99 which means less people are going to buy it regardless of how much more "cool" it is that you can download games from PSN.
Sony in particular probably wants to stay away from this, given that a lot of us already own a ton of PS1 games on PSN and given the PSP->Vita licensing fiasco they went through probably wouldn't be too keen on letting us download those games on yet another system for free. Nintendo's probably in the same boat with the NES and SNES classics considering how many people already bought extra virtual console games on the Wii and Wii U and would feel ripped off if they had to purchase them again on yet another system.
I'm 100% confident that these options were on the drawing board from the very beginning, and were likely shot down due to the fact that the costs of doing this wouldn't ever be recuperated.