5G fixed wireless makes sense in urban and suburban areas because a single tower can serve many customers. But in rural areas, the number of customers per tower is much lower. To be profitable, the cost to build & maintain the tower must be covered by the customers in the area. Google says a 5G tower can cost anywhere from $150k-$300k, with maintenance costs being around 10% of that per year. In rural areas, the cost is likely on the high end because power and fiber lines will be longer. Each 5G tower has a range of 5ish miles, meaning it can serve an area of 75-80 square miles. A rural county like Ferry County, Washington has 2 households per square mile. So in that county, a tower can serve 150-160 households. Assuming 100% of households are customers, that means each must pay $200-400 per year for the tower to break even after a decade. The actual numbers are fuzzier. Obviously you won't have 100% adoption, but cell towers also serve cell phones.
In comparison, each Starlink satellite costs around $1 million to manufacture and launch, and each satellite lasts at least 5 years. So cost per satellite per year is $200k. They currently have 7,600 satellites serving 7 million customers, meaning on average, each satellite serves almost 1,000 customers. At $200k per satellite per year, each customer needs to pay $200 per year for them to break even. It seems likely that launch costs will go down in the future, meaning this number will decrease.
There's also the complication that each new Starlink satellite improves coverage & bandwidth for the entire globe, while each new 5G tower improves coverage & bandwidth in a specific area. A county may have a population density of 2-4 households per square mile, but many of those households are clustered together. The less dense areas are not likely to be covered by cell towers any time soon, as it's less economically viable. Another disadvantage of cell towers is service failures. A single Starlink satellite failure means a slight degradation of service, while a single cell tower failure means everyone in the region is taken offline. In areas where both services are available, people would be likely to prefer the more reliable option.