prayer mats

why do people pray on mats. i know it sounds like a dumb qn, but i don't get the logic behind it. i get if say the ground is too hard, or if your praying outdoors, or something, but why do people insist on using them inside? i mean the grounds clean and all, so why?

Ahan nice but unlogical Qn...??!

well bcoz Prayer mat is clean then other Surface for prayer in mosque...n muslims perform prayer in a que(SAF) bcoz of Prayer mat they stand together with a small distance B/w each person... hhmm
i think dat is above main reson..!

If there comes a reason or necessity to read Salaah outside and there is grass then we do read on it if we have nothing else.
Reading Salaah on a mat always is safer as of fear of any naapaaki (uncleanliness) being around.

Hope that helps explain