I have several examples that vary from thinness to thickness:
Dell Inspirion R15 from 2012 year
Lenovo G555 from 2011, video died from heat, new motherboard has external fans.
Acer Aspire 5610 from 2006
HP Elitebook 2740p convertible laptop/tablet (touch screen spins 180) from 2011
Dell Latitude CPxH-500GT from 1998 that is built like a tank, cannot fail.
AST 10" Ascentia J30 P100 from the mid 1990s, also very sturdy.
Once screen illumination switched from fluorescent tubes to LEDs, the top part got thinner. Then the new drives and batteries, chips on boards in base half got much thinner too. Too bad the keyboards turned to crap--I use only USB regular desktop keyboards and mouses now.