a new liner is very pliable and has relatively high elasticity, it is able to form to whatever shape your floor is even if it seems as though there is not enough liner to accomodate.
the water pressure on the liner over time will actually compress the vinyl some which in turn adds to it losing it's elasticity and the sun's UV rays also dry it out.
When you drain the water, the liner will actually shrink some - pulling off the floor/walls a bit - if you refill, it will tear somewhere because it no longer has the elasticity it had when it was new and will not go back to the shape/size it was before you removed the water.
I guess you could reuse it if you somehow figured out by how many % it will shrink and accommodate for that by raising your pool floor that % and shrinking the diameter by the same...
A friend once drained his Inground pool completely for 2 days to scrub it - when he told me what he did I said uh-ohh...he said - it'll be fine.
He refilled it and before it was even close to full, it pulled the entire liner out of the track - he had to buy a new one. Had he kept a few feet of water in it, he would have been ok.