Washing your face is a very important step when it comes to removing oils, dirt, dead skin cells, and other things that build up and clog your pores and glands. Even though its an important step, it doesn't always have to be done in the morning.
Washing your face in the morning usually depends on a person's skin type and their preferences. If someone has acne-prone or oily skin, its more beneficial for them to wash their face in the morning in contrast to people with sensitive skin, excema, or rosacea who find that washing their face in the morning makes it feel dry.
Stephanie Saxton-Daniels, MD, who was interviewed for the Health article states that "“It’s important not to overdo it,” she explained. “Stripping the skin of the natural lipids produced overnight can compromise skin barrier function, making the skin more susceptible to irritation.”" For people with sensitive skin, this can be very helpful to avoid irritation and only cleansing at night is enough.
CeraVe states that "Washing your face in the morning is important because it removes sweat, excess oil, and bacteria from the night, while evening cleansing removes dirt, oil, makeup, environmental pollutants, and other impurities that build up throughout the day." This shows that washing your face at night and in the morning are equally important, but its overall up to someone's skintype and how they react to it.
Sources:
https://www.cerave.com/skin-smarts/skincare-tips-advice/should-you-wash-your-face-in-the-morning
https://www.health.com/should-you-wash-face-morning-8597820