It's more likely they just lack either spectrum and/or backhaul to the tower where they are. For example, TMobile in many areas has only 1gbps to many towers despite sharing that spectrum across 3 or even 4 sets of panels. Where I am, the spectrum itself could easily support 1.5-2Gbps or more per sector on the tower, but they'd need at least 10Gbps to allow each sector to max out the deployed spectrum.