Pedal-powered fat bikes may not need suspension forks. The tires have considerable compliance due to the increased air volume, which suffices in most riding conditions.
Compared to standard bikes, fat-tire bikes are heavier and more difficult to pedal because of the added weight and rolling tire resistance. Some riders may determine that the added weight of the fork does not justify the performance.
Electric fat-tire bikes are different in that bikes can travel at much higher speeds when the pedal-assist is activated. Electric bikes are also much heavier, and forces from bumps are more pronounced. The suspension fork will help absorb some of these bumps and give a smoother ride.
Suspension forks also allow you to inflate the tires to a higher pressure, leading to increased efficiency on pavement. The suspension fork will provide compliance when inflated tires would normally result in a rougher ride.