This was my first thought.
Just two days ago I was very aware of this effect, being in an area of very low cell service demand save for a dozen days a year when demand just plain swamps the towers. My phone drained the battery fast just trying to maintain a basic connection and determine location; well before it died I gave up using it for inability to even log in to the Find My Friends app for more than 2 seconds at best, and it thrashing between LTE, 4G, Edge, and no service. ...and that was without the teeming horde panicking & calling 911 and friends and uploading videos and...