after modelling an object for a while and performing certain operations on it... if you open the Attribute editor...take a look at the tabs that are there before erasing history...and the ones that are there after... only the basic ones remain....basically all the tabs that you lost after erasing history you cant edit anymore ............example...create a poly sphere, you can increase poly count in the channel box, delete history, you lose the ability to do that...you'll basicall have to use split edge ring tool or something

-another case you wouldnt want to erase history, is after creating wrap deformers....they wont work anymore