If by that you mean does your non-law component dictate what area of law you end up practising (I'm not sure if that's what you're asking or whether you mean employment beyond being a lawyer also? but I'll answer on that basis) -
In short - no. It may help inform you better of the context of your work. Eg an ex-colleague completed the same degrees as me (being a non-law degree of Business majoring in HRM and IR) and she said that it was really helpful as her transition to working as an employment and OHS lawyer was smoother, she felt, than for other new lawyers because she had an understanding of why things happen and what causes them as opposed to just understanding how the law applies.
But it is by no means necessary/a prerequisite in all fields. Eg I am yet to meet a criminal lawyer who combined law with a Social Science (Criminology) degree
and my employer who is a fairly well renowned family lawyer has on several ocasions said that whlist it may be beneficial to understand psychology and child development, by no means it is an absolute necessity to combine law with a Psych or Early childhood degree or social work degree to be a good family lawyer.
That said though, there may be occasions when it is necessary for particularly specialised fields where an understanding of the technical side of things will assist, such as.... i don't know... perhaps some medical fields? or fields related to the use of scientific materials and processes?
Don't forget too - you choose electives in your law degree
So if for example, you wanted to practice criminal law, you would choose electives that would provide you with that knowledge.
