Beer Plastic Bottles

Why exactly beer in a plastic bottle is not considered so good?
Why exactly beer in a plastic bottle not considered as good as glass or tin? What exactly is the difference?
When I started homebrewing, I my beer bottled in 16 or 20 oz PET plastic "1" bottles. They are food grade and not disclose any flavor in the drink. That's why we get water, sodas, etc. juice in the bottles. There is nothing wrong with plastic bottles, as long as the beer is drunk in them is worth, rather than Bud / Miller Coors junk that many people insist to drink. In fact, I guess I get a thumbs down in a few here just because I dissed that kind of beer drinkers.
Beer In Plastic