taking assignments that are outside of your niche can help you expand your horizons as an artist. There is no shame in doing this, and you can easily use the money to support doing the type of photography you love.
I loved doing photojournalism in college, because it made me tackle subjects outside of my niche. It made me think about the entire world more in terms of photography and broadened by horizons.
I learned the art of the moving portrait, where you'd get subjects (most easily visiting dignitaries), who weren't posing for you, but instead, you needing to move around them, instead of them posing for you.
If you are ok with shooting it there is nothing wrong with shooting outside your niche, however, do not put those photos in your portfolio. Your portfolio should be a reflection of your niche or target nice.
Honestly, only you can answer that. But is photography your only income? do you make enough money from the photography you love vs portraits? Photography as a business is like any other business, sometimes you love it, sometimes you just gotta do it to pay the bills.