Why did all mega carriers stop using manual transmissions?

Fuel economy.
That's what all the mega's have stated.
I drove for a large hazmat/tanker company and the company switched from stick shifts to automatic transmissions, to save on fuel costs. We were told a massive amount of money was saved on fuel costs. We ran 48 states and Canada.

 

Driver recruitment, and maintenance involved that's often caused by misuse.

Cheaper to run auto's, especially nowadays, at least for large places.

O/O who cares about maintenance and life of service, the manual can't be beat

 

I've been told that fuel is EVERYTHING for the megas, especially considering the way the diesel prices have been the last few years. I was one of over 8,000 drivers at Prime...you multiply even a fraction of a MPG in savings and there you go.

Also one less potential sticking point for training...gets fresh meat into the seat quicker.

 

Like @Chinatown says. Autos were sold to save fuel. They also allow companies to hire people that can't drive a stick to come get paid to stare at their smartphone 23 hours per day.

 

They all say that but I drove 2 of the exact same trucks spec'd exactly the same, minus the trans, and the 10 spd manual got better mileage than the 12 spd auto

 

So they can put anyone that can fog a mirror in the drivers seat. They are less likely to damage an automated manual.

 

That's because you know what you're doing.

When you look at a scatter plot for our fleet, year over year, pre autos the best fit curve made a left skewed bell curve. As we transitioned, the curve shifted to the right and began to tighten. Those who traditionally topped the mpg leader board dropped, but everyone else was forcibly dragged up. The range between top and bottom performers is much smaller, and the fleet average is significantly higher.

The other thing I noticed is around 3 months into my first auto they changed the programming and my fuel economy went up
I also learned how to drive the dang thing, so I don't know which factor had the larger impact.

 

Sitting there; seeing the terrain, hearing the exhaust noise level, feeling the drag increasing. Then smoothly selecting the appropriate gear will always beat a staged/programmed box. Especially in those pulls where a knowledgeable driver knows he can lug down 10 RPM longer and it will level enough to pick back up and go on to the top in the present gear. (Proviso.. This is predicated on you having a driver in the seat)

 

This sums up most of it. The slack jawed nose picking droolers got a huge bump in fuel economy since the auto could cover just how BAD they are at driving, while the actual drivers got a cut sadly the droolers outnumber the drivers 80 to 1 at best so...better to kneecap the few actual drivers then the ocean of steering wheel holders.

Additionally it opens options to hire as others have said since even the low bar to having the brainpower to use a manual is now gone. This also saves on repair costs since these idiots dont torch the clutch and clutch breaks or blow out bells and drive lines. There is also the fact so many of these so called "drivers" have so little brain capacity to begin with that even expecting them to be able to do two complicated things like shift and look for a turn is too much to ask.

Dont belive me go watch youtube. There are MILLIONS of examples.