They send that because the once-a-year travel all have a different expectation and time requirements to make a flight.
Here is my typical Monday morning for an 8:30am flight:
T-180: Wake-up, Get in 5 Mile run,Return, shower, grab breakfast
T-90: Leave House, drive to airport
T-50: Enter Parking Garage, walk into terminal
T-45: Enter Pre-Check Line
T-40: Through TSA, walk to gate, rest stop
T-30: Arrive at Gate
Here is the typical once-a-year traveler routine. No joke this is their routine. They are the people that need to be there to set-up camp in the gate area before I've even left the house for the airport.
T-300
Leave house, stop at McDonalds Drive-through
T-240:
Park at off-site parking
Unload 6 oversized bags
Wait for Shuttle
Ride Shuttle
Unload Shuttle
Multiple elevator rides to departure level
Get in wrong line to check bags
Stare confused at kiosk
Ask for help
Get in proper line
Wait in line
Not have the proper documents
Unstuff and repack overweight bags
Fumble with credit cards to pay bag fees
Check bags with agent
Act confused about security line to use
Fumble with carryon bags
Attempt to get in Precheck line, get send back by agent
Get in proper security line
Wait 20-30 minutes in security line
Fumble with ID
Fumble more with carryons
Unpack everything for TSA
Remove shoes, belts, wallets
Remove $5 of change from pocket
Set-up detector
Get selected for secondary screening
Wait for secondary screening
T-180
Clear security
Fumble with carryones
Use bathroom
Eat at a sit-down restaurant
Stare at gate monitors
Ride the tram
Stand on moving walkways
Use bathroom again
Find gate area
T-120
Set-up camp at gate area across 10 chairs
Fumble with carryons
Charge every electronic device using all available plugs
Use bathroom again
Go buy more stuff from the newsstand
Go buy more food to carry-on to plane
Use bathroom again
Fumble with carryons
T-60
Stand up to be gate lice
Use bathroom again
Be ready to board
Attempt to board in wrong zone