I agree up to a point, but the exterior appearance is essential as well. Because if the look of this site is beautiful, it will make a good impression with every individual and they will have interested in this building. Hence, it is not certain that the the purpose of using is more important than the appearance outside.
Firstly, if people use some buildings with the right functions, it will bring many advantages things for them like their buildings will more develop and gain some achievements in their domains. For example, if the schools are used with the appropriate target, it will pay student’s attention because they have spacious space and it can help the students too much in studying and inspire them to go to school and school also assist their students on unleashing their creativities. That’s why everybody must focus on your intended use but whether it is attracted some famous companies or the workers.
Thus, it also depends on their appearance too. Because the first impression is the most important, if the structure is good and it looks like spacious and eye-catching the individuals, it will bring the best efficiently for the investers. If the architect is not properly with almost the aesthetic perception of people, it will have some bad comments and lead to many drawback things such as your work can be prevented by a few bad factors and it also affects on their reputations on this fields.
Finally, I think both factors is necessary because if the building can have both conditions, it will meet the requirement of market and perhaps it can make a big profit for your building.