Are there any reasons why Macro lens could or should not be used as a landscape lens?
Are there any reasons why Macro lens could or should not be used as a landscape lens?
No, none at all.
While Donald is undoubtedly right in theory, I'm not sure how true that answer is in practice. The only macro lens that I have is the Tamron 90, and it is very nice for macro or portrait work. However, it has a very substantial LoCA problem when used as a general-purpose or landscape lens. Furthermore, it seems to have serious problems focusing at mid-distance and beyond. I suspect that these things may reflect being optimized for macro-to-close distances, but I may simply have gotten a bad copy of the lens. FWIW
Test your lens with a landscape image and see if the results are acceptable for you. Your lens may produce different results than someone else’s lens. Whether it is photography, food, music or whatever, it's the results you get (or don't get), that are more important than the specifications.
I agree with Frank. I have used both my EF-S 60mm macro and my EF 100mm L macro for other purposes and have not noticed any problems. Both focus fine at long distances. However, I have not looked specifically for CA. Try it with your lens and see what happens.
I was going to suggest to check a benchmark in http://photozone.de/ but then I remembered they only check at one magnification for each lens; how useless!.