Cover lifters perform two main functions, they keep the cover free from damage (covers used with cover lifters invariably last longer than those that don't) and they help ensure user safety - an important consideration for every owner (and a critical one if the hot tub is used in a commercial environment).
Covers are bulky, cumbersome items and trying to move one 'freely' usually requires two people and/or a fair bit of effort. With a lifter in place things become a lot easier: One person is able to open and close the cover with a minimum of fuss and in complete safety, and, once opened, the lifter parks the cover neatly out of the way. Job done!
Without a lifter though, the problems are likely to continue and it's a fact that a 'loose' cover is most likely to sustain damage when it is actually off the tub. Apart from the knocks it may suffer when being moved, it's liable to be left in situations that can lead to damage: Left upright it can fall / get blown over, left on the floor it can get stood on, sat-upon, or used as a human or pet sun-lounger.
Also, when finally it's returned to the tub, it may have picked up dirt that will inevitably end up in the water.
All good reasons why smart hot tub owners invest in a cover lifter!