Buying is cheaper than restoring. And if you just make salvage rare, you incentivize savescumming. Salvage being plentiful but only giving out exclusively (or almost exclusively) d-mod ships, means you both get a viable D-mod salvage playstyle and it's also a way to get rare or specific ships easier, at a higher cost (with restore).
Yes buying is cheaper than restoring, which also makes little sense from a beginner standpoint, and is also another "feels bad" of the system. Rather going "oh wow i salvaged this cool ship, and while it's got dmods I can fix that" it's "meh scrap it for parts and i'll find it in a store."
How does making salvage rare incentivize save scumming any more than having random ships available for sale? Those who will scum will scum. Arguably it's less incentive since winning a battle repeatedly is harder than opening a shop menu.
Further I feel that the whole point of the industry tree should be to make salvage more plentiful, and maybe targeted (pick ships pre or post battle that are more likely to be able to be salvaged) so there's some actual 'Game' involved rather than rng.
The viable dmod playstyle sticks around (and is now more tied to the skill tree that directly relates to it), and you can still get rare or specific ships (at a lower cost, which makes sense given part of the cost is repairing your fleet after defeating them).
The current system really isn't intuitive at all and I think ruins some of the better moments like seeing a cool ship for salvage (this also goes hand in hand with how easy it is to find ships in stores) , and instead turns the salavage screen into a formality 90% of the time (click to open, nope nothing good, salvage, repeat the next 20 times).
All that said, I get that larger economy tweaks aren't easy, and there may just not be worth it, but maybe with the world shut down I'll take a look at seeing what I can do with mods, because I really think it'd be a great way to tweak the core play experience