Because protons are already intrinsically almost 2000 times larger than electrons. Inventing new basic particles of matter is not a very good call in this situation mainly because you'd need to define a means of production (by the way, atom splitter technology, which we already have, would be much easier to shrink to the appropriate size than a technology we've not even conceived of yet), a method of storage, and every interaction said particles would have with everything in reality and physics.
Also, how would you store these particles, if they strip the protons from matter?