Why cant i get rid of the black bars on my widescreen tv, ?

I have a 55 inch led tv, why is it if they converted into widescreen mode why do u still get the black bar at the top n bottom of the screen, when I had the toshiba projection widescreen, great picture, ahead of its time, I could change the size of my pic in 6 different ways, also get rid of those black bars. I've bought 2 tvs this last year1 cd, 1 led but I can't change the size to get rid of the black bars. I paid way more for these newer tvs, I only paid $1600 for my toshiba projection tv 7 years ago and it seems like there was more features than my new ones?? I used to be a professional audio, video installet and restore cars years ago and I can't even figure out how to hook up my surround on my led, the smaller version of my led tv has it marked on the back but not on my 55 inch. My kids lost the manual.