Where i live an SMS costs me $0.15. the cheapest internet flat (unmetered) costs me $4 per month. There are plans with unlimited SMS and domestic calls include

Where i live an SMS costs me $0.15. the cheapest internet flat (unmetered) costs me $4 per month. There are plans with unlimited SMS and domestic calls included, but they are like $50 per month. Why would i pay that when everyone is on WA/Signal anyways and i can just buy a cheap data sim with unmetered bandwidth?