The ready made ones I think often are self-adhesive (like aftermarket scratchplates often are), and the instructions mention filling bad damage on the inner bridge plate with eg an epoxy before fitting (or repairing th plate).

Claims for the ready made ones include a better, less soft, contact and therefore better energy transfer - a bit like those endless arguments about brass bridge pins, and I am utterly convinced I can hear extra brightness from brass bridge pins.

Next time you change strings Giok, I suggest you have a feel around where the ball ends sit, or get a mirror and torch in there, and I think you will probably be horrified at the state of the inner plate. It wouldn't happen so much if the inner bridge plate was say ebony, but it usually isn't. There's a page at the Stew-mac site talking one throught he repair, and to me it looks like an ounce of prevention being worth a pound of cure.