A reel that is set for some contact probably has a good relief angle ground into the blades. That means the reel runs with less friction and enables it to cut like scissors. Many mower shops grind off all of the relief angles by simply spin grinding the reel. Then you are forced to run the machine with zero contact and are unable to back lap to maintain the edge. A spin grind only reel means the reel has to be reground as soon as quality of cut has declined. I notice that spin ground reels get dull rapidly when cutting bermuda, seashore paspalum or zoysia lawns. Lawn services with reel mowers sharpened that way get less than a month out of their machines before they start tearing grass or jamming. A zero contact spin ground mower might be ok for bent grass on a putting green, most lawns are not bent and they are not cut every day.
They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety.
Benjamin Franklin 1775
Sell not virtue to purchase wealth, nor Liberty to purchase power.
Benjamin Franklin Poor Richard's Almanac1738