Purpose of BCD

Apparently, Binary Coded Decimal was an important feature in early CPUs. Can someone explain to me what its purpose is? I know that it makes it easier to print decimal values to a screen, but really, converting a binary integer into a string of decimal characters and vice versa are trivial problems. Is it really worth the extra CPU complexity and decreased data density just to give the programmer slightly less work to do when printing decimal numbers? You would think that with memory being so expensive back in the day, engineers would be more motivated to conserve its use.

I use HP42S emulator that uses BCD internally to avoid errors with inexact values that might be caused by binary representations.