As you may have heard, "Coin collecting is the hobby of Kings". When Proof coins were first minted, they were for the dignitaries, government officials, or given as gifts by our government. If you weren't worthy of a gift, well, you had to buy your own. How cool is it to have a coin struck from the same dies, same materials, and at the same time, as an example given to a king. In many cases, the rarest and absolute best example of a series or design to be minted, is the proof.
Why would you want to circulate Proof coins ? By not circulating them, people are then "collecting" them for various reasons that other people, for various reasons, would not understand.
Why collect uncirculated coins? Why collect CIRCULATED ones? Why collect anything? Why not spend ALL coins, thus circulating them, and collect the stuff we buy with them? Which some of us do, I guess. Each to personal desire I guess.
Obviously you have determined that being "for circulating use" is a dispositive attribute. Congratulations for deciding what works for you. Others do not feel such is an important attribute. I'm weird. I collect proofs of "regular" coins, but not proof commemoratives so much. In modern commems, I concentrate on the non-proofs, and ALL of those are not made for circulating use.
You have something against the gold and one silver tribute piece? I don't buy gold at these levels but they're pretty.