Never had many bumper stickers. I think partly because a couple years out of college I started driving a company car for work which was also provided for my personal use as part of the compensation. Of course stickers, decals, and such were prohibited. Didn’t even have a company logo on it. 20 odd years of that probably had some influence on not flying stickers on my vehicles. Kind of like tattoos, nothing against them, just not my thing.
People have made assumptions about me based more on what I drive. When my company car was a Crown Vic (had several of those over the years) many people assumed I was LEO (I wasn’t). For a while I had a Chevy Astro van as my company vehicle and people thought I was the cable guy (I wasn’t). Now I’m driving a white 4WD pickup, work truck trim package, and I get random people assuming I’m some sort of construction tradesman (I’m not). No shame in being LEO/cable guy/contractor IMO so never bothered me.
I did have one, and only one bumper sticker. I had a Nissan Frontier 4WD. Replaced the front bumper with a winch bar and rear bumper with a matching “off road” bumper from Schrockworks. It came with a bumper sticker which I tossed aside but didn’t throw away. Stuff like that for Frontier’s wasn’t easy to source at the time (maybe still isn’t). I had MANY people ask me where I got them. People left notes on the windshield asking me to call them to tell them where I got them. To make it worse, when I said, “Schrockworks” most people thought I had a speech impediment so I had to spell it for them. After a few months of this, I found the Schrockworks bumper sticker that had their phone number and website on it and stuck it on the right end of the winch bar. No more questions.