I also bought dimming stickers. I can’t tell you why everyone uses them, of course, but I bought stickers rather than using tape for a couple of reasons. The main one is that there are some lights that indicate information I still want to get. Our fan has LEDs to indicate current speed, my wireless phone charger has a light to indicate that it detects the phone. That information is good, and I want it! Just not as brightly as the manufacturer wants to give it to me, so I put stickers that dim about 75% and they’re perfect. The other big reason, for me, is that I simply find the stickers more aesthetically pleasing. Even if I want to block the light fully, rather than just dim it, a little circular sticker looks nicer to me than a piece of tape.
I’ve been using these, but I’m sure there are many other choices that are just as good!