Buggy fronts are kinda odd. I'm going to assume we are talking about 1/10 2WD fronts, since they are the most different from the rears. Firstly, they're super-skinny so that immediately limits the amount of creativity you can shove into such a narrow tire. For a looong time we just ran rib tires on the front of buggies (and stadium trucks). Back then every track was loose and fluffy so the ribs helped "bite" into the dirt when the wheels took lateral force. This generates good side-bite by having a sharp edge to get into the soft dirt.

Now, tracks have taken a sharp contrast and most 1/10 tracks are hard-packed and high-bite. So, now we need a different style tire to keep up, but the tire's profile hasn't changed in 30 years. Now, we commonly run tires with treads, pins or slicks.

To answer your question more specifically, why don't we run the same tread front and rear on buggies, it has to do with balance. When tuning any kind of car, r/c or otherwise, there's never a perfect setup that gets you the exact amount of traction, stability and control. It's always a balancing act to level out those characteristics into what makes the vehicle the most comfortable to drive fast. A lot of the time with 2WD buggies there is steering to spare, so you likely won't need an incredibly aggressive front tire. This is more true when looking at mid-motor buggies. The weight distribution gets moved further forward generating even more front grip. So to balance it out it's common to run a less aggressive front tire.

I personally run slicks (really just worn-out bar tires) on the front of my 22SCT 2.0 short course truck. The same idea applies. That thing has way more steering authority than I can comfortably use. I dial back my dual-rate on the transmitter and run bald tires up front to help calm the steering down. If I had more front traction I'd be taking balance away from the rear end of the car and potentially oversteering corners and breaking the rear end loose.

Hope this makes sense or at least gives a bit more insight.