So that there are no complaints about VK in the spirit of "you give nationalists an excellent opportunity to easily find each other! 11". After all, clicking on someone's political views on the page opens a search for people with the same views.
Any information about yourself, any sort, so to speak, opinions can be indicated in the "About me" section.
Probably due to the fact that nationalism itself does not correspond to any specific political ideology. A socialist, a conservative, a liberal, and even a person with indifferent political views can be a nationalist.