Flying at FL90 or FL100 I spent more than 80% of my time in clear air.
No doubt a conservative weather strategy (even more conservative than mine, which most pilots I know think is really conservative) would deliver VMC at FL070-100 every time. But you say you are not doing that.
If you are flying a deiced twin with radar (you don't say but if PT it would be something like that) and paid to fly (i.e. get the sack if you don't fly) then you will go anyway, and often you will find "VMC" at FL070 within a layered cloud whose tops may be FL140, but whereas you will be happy with that, and anyway have to be due to lack of oxygen for passengers, I will be working hard to stay above those tops because I am not de-iced and thus cannot afford to get snookered down below in solid IMC and collecting ice, whereas you can just do that.
I have no idea how often I am flying at say FL150, 2000ft above a solid overcast, while somebody could be flying below me at FL070 and be in VMC either between layers or below the cloud. But to me that is irrelevant because I cannot afford to get stuck down there, whereas you have no choice and I am sure that a lot of the time you will find some VMC down there. To me that is academic because to fly down there would be foolish as it would cut off my escape routes from icing.
When hacking around in Class G one can always try to descend to warmer air but on an airways flight this is an option only up to a point, before ATC gets ratty about it because one is going into some military area. One can declare a mayday or just firmly request a descent as it is obviously an emergency, and I had to do that recently (freezing rain, but in IMC and descending close to destination anyway) but one doesn't want to be hacking 500nm right across a chunk of Europe at 3000ft, with the VFR chart, wondering what obstacles are down there. So the only smart way is to be on top and stay there.
Icing is pretty statistical and I can well believe that one gets it substantially only say 10% of the time. The other day I went up in in about -8C and after some minutes collected about 5mm of mixed clear and rime. How much would I pick up after say 3 hours? I don't really want to be stuck in IMC finding out the answer. I want to be upstairs in sunshine, with 100nm vis, knowing there isn't any ice down there.
Also you don't say anything about what you fly. If you are doing 200kt TAS then you are getting an aerodynamic temp rise of 5-6 degC and that narrows the supercooled water temperature band by 1/3 to 1/2.
I think to argue that icing is rare is missing the point - for a non deiced pilot. Sure it is rare. I know a few pilots who say it is rare so why bother about it? But I could post pictures of heavily iced up wing leading edges taken by people who nearly got killed who banked on it being rare. There are many more who did get killed but there are no pics because the stuff melted before anybody got to it, or melted in the fire. That's the problem with writing a few lines attacking somebody's strategy, without posting any detail.