Two of those sets are strictly reprints, but Antiquities and Legends gave us 414 cards, which is actually more than 2004 and 2014
For just one mana you get a bit of burn damage as well as a Blood token you can utilize later
Various other rules throughout the document have also been updated to accommodate battles, including rules for combat, counters, types, state-based actions, and so on
Unlike some other formats that use only old cards, you are encouraged to use more recent printings and if you want to proxy, I won't stop you
"You just don't see a lot of them on the market right now
Any creature you have that comes in afterwards gains a +1/+1 and haste, so it helps to improve commanders that cheat creatures into play but dont grant haste themselves