Putting out another sub-patch, say 1.7.4 or whatever, would mean both testers and coders would have to focus on that and not 1.8 for some period. Which in turn would delay 1.8 or make it less polished. Which is something that may be worthwhile in some circumstances, but (I can only assume) it has been judged that the impact of this issue, restricted to that tiny proportion of our players who run the game without Steam, meant that was not enough of a reason to delay the patch or to allow it out with reduced quality. The calculus would be, I think, the benefit of the (say) 1% vs the 99%.
Yes, ideally every found bug would be fixed and a patch released upon the instant (as
delpiero1234 would run a software company, it appears), but it just can't be that way - no-one does this. In PDS's case major patches are funded by their accompanying DLCs, and if they spent a year or two just releasing small bug-fix patches every few days (so no DLCs nor major patches) then the EU4 budget runs out and the game is dead.
The money from the DLCs funds the development of the major patches and the QA people to test the minor and major patches and the DLCs. Bugs that aren't show-stoppers have to be assessed for the impact of not fixing them AND the impact of fixing them. At some point you have to call a halt to testing and refinement and let a game/patch/DLC out of the lab, otherwise
you end up like Mark Twain - broke but still no perfect product.
Note the above is just my assessment of the situation, I have no deep insight into the actual thinking that went into this. My point is there is a cost to everything, and a policy of patching every bug all the time has its own downsides, which I'm not sure you'd be happy with either.