But so far I haven't met proper mathematician who doesn't type *, x or dot between variables.
Well, I guess that means I don't know my math? Anyone who is a 'mathematician' knows what XY means. If you start typing XxY, then shit gets confusing. Is that X*X*Y, and you simply forgot to capitalize the second? Is it multiplication (X times Y)? Outside of programming languages, "*" is almost never used, simply because it is not actually a math symbol. If you try and type up any professional report using an asterisk, people will laugh at you, or if it is being submitted for grading, you will most certainly lose points. Same goes for using an x for multiplication. It is too easy to confuse with another variable. Therefore, the only acceptable forms of writing X times Y would be XY (or I suppose X(Y), although you rarely see that, since it could be confused as the function X of Y), or X dot Y. X dot Y may be used in the most 'professional' of reports, if only because it takes a lot more time to find the proper "dot" symbol unless you have a newer Microsoft Word program.
Tl;dr: You must have not met any true mathematicians, or you have only met some code junkies, since * is only acceptable in programming.