I think that wearing a parachute falls into the "keep your options open" category. It can never do any harm (although I bet this comment elicits a reply that will attempt to refute it!).
When I first started flying a certain large piston type (P-51) and displaying it, I did not wear a parachute because the owner did not leave one in that particular airframe. On my fifth sortie in this machine, I suffered a dropped valve rod and a considerable loss of power. Luckily, I was close enough to home plate to land without further damage (albeit on a runway that we had declared unsuitable for a normal landing with the prevailing wind, but that is another story). After the engine change, I always wore a parachute, even though I had been too low to bail out when the aforementioned engine failure occurred; you never know what will happen next. In fact, the next incident I had in it was ruder tab buzz (which coupled into rudder flutter through the anti-balance tab mechanism) on the Vne dive during an airtest. I was close to losing the rudder and could have had to bail out. Luckily, again I landed safely but felt much more comfortable knowing that bail out was an option.
"What ifing" is one of the great airmanship tools in avaiation, and I am sure that we can all think of "what ifs" when bail out is the best, and perhaps only, option.