There is no right or wrong answer.
Sexual libido varies from person to person and couple to couple.
Naturally if you have one person who wants sex 4 times a week and their mate is content with once a week there are bound to be issues. That's a difference of 208 VS 52 times per year!
Having said that there are instances where people are fortunate enough to find someone they're in sync with but things could change down the road. Menopause, erectile dysfunction, other health issues, and overall marital disharmony can effect both the frequency and the quality of sexual interactions in a marriage.
If it's an issue of actual dissatisfaction communication is the key in determining if their mate is willing try doing things differently.
Having said that communication is not an ask and it shall be given proposition. He/she simply may not be see it as a priority.
Some people simply miss having variety or being surprised.
They find themselves always doing things the same way.
Monogamy becomes boring when couples become lazy.