The first explanation that comes to mind for me is that perhaps it's because executives often own all or part of the company(ies) they run. They *pay* their employees, but they *compensate* themselves, the difference being that the draw that an executive takes is often just necessary living expenses and bonuses as needed; the work that an executive does is--ostensibly, at least--aimed toward increasing the profitability of the company, whereas an employee is--generally, at least--working just to get paid.

Although I think you're right, as far as it goes, on the vanilla end of the spectrum, I'm more inclined to agree with the perquisites, etc. explanation. An Executive may be given stock options as part of their compensation, in which case, its interest in the firm can't give rise to compensation. Tax advantages link neatly with the suggestion of superiority attaching to the word. One is compensated for something lost, one is paid for something one gives in barter. Unlike the wage earner, the executive seems imagined to have an intrinsic value by its own right. The wage earner, in contrast, is inherently worthless.

Mexico, incidentally, also has a very progressive constitution--sometimes I wonder if the will to enforcement isn't equalizing on both sides of the border.