Do not mix old and new batteries! Why?

Question

Its always written on things like remote controls etc etc donot mix new and old batteries.

The other day my remote wasnt working due to low batteries. I used 2 new and two old batteries and its working fine ever since. So whats basically the reason?

Answer 1

bc it will send diff. voltages to the moter in the electronic device wich for some reason that idk is bad for it  hope i helped  C:

Answer 2

The old batteries will go dead sooner, causing increased resistance and drain on the new batteries and thus shortened life of the new batteries.  They'll work for a while, but best not to mix them so that you get the most life out of the batteries.  The older dead batteries are more prone to leakage when the current from the new batteries is passing through them.

Answer 3

"the man" wants you to just buy all new ones instead of saving money.

But I'm sure it probably has something to do with drawing more energy from one and not enough from another, but chances are that isn't going to do anything bad