Both front abs sensors fail at same time?

I have a 1997 Chevy Suburban 4x4 3/4 ton with a 7.4 engine with 127,000 miles. Recently, while I was coming to a slow stop at an icy intersection I felt the abs start to kick in as usual for that type of stop, then suddenly the abs brakes quit working and the abs light came on. I had a diagnostic on the vehicle done at two businesses. Both indicate codes C0022 and C0026 which are both left and right abs wheel sensors. One business indicated that it found code C0021 R/F CKT, OPEN OR SHORT TO GROUND-COO22 R/F SPEED SENSOR SIGNAL MISSING-C0026 L/F SPEED SENSOR SIGNAL MISSING. An attempt was made to clear the codes but it returned (hard fault)... I am willing to repair the system by replacing the wheel sensors but I have two things that I am concerned about. One, why would two sensors go out at the same time and secondly, what is to say replacing the sensors is going to fix the problem. To me, there has to be another problem that would cause two sensors to go out at the same time (Code C0021 R/F CKT, OPEN OR SHORT TO GROUND?). Both of the Chevy dealerships say that I need to replace both sensors.