Well designed plasmas don't burn in either.
I've repaired 8 x 2007/2008 Panasonic FHD 42"/46" plasmas, varying amount of hours from 4000~18000 hours.
Plus a Pioneer Kuro 9th Gen 50" panel. Made for watching movies (21:9 etc) due to cinema reference panel and has been doing so for at least half of its 12,500 hour usage time. So you'd expect burn in from the movie bars on the 16:9 screen.
How many had burn in? not a single one. I mean seriously. You can put these TVs on a full white pattern and every pixel has the same intensity, no dead pixels either.
I did have two LG plasma with some faint burn in from the Cbeebies logo (UK childrens channel.) The LGs seem to be the worst for burn in, not sure if this is a design characteristic or just a fluke. LG's plasmas have always been fairly basic units, with decent build quality but average performance in the best of cases.