Re: Pedantic spelling
I guess people are lazy and just want to type the fewest characters possible hence 'maths' ?
If you do the m, you'll find "m" is even cheaper.
(On a more serious note, the thesis quoted above is prima facie incorrect. People will use the term they're accustomed to, which will be the term predominant in their speech communities. Just as with any other regional variation in diction and usage.)