Deer get used to cars and trucks , farm equipment , and even ATV's if they keep a patern of where they're used.
I used to see deer all the time while working fields with a tractor , they would let you get close also.
If you stopped , they watched you , it you shut down the tractor or got off it , they were gone.
While running a trap line with an ATV same thing ,they watched you and wouldn't run unless you stopped and got off.
This is true, In fact they get used to individual people.
I know an old lady that fed the deer, within seconds of her coming out of the house the deer would trot out of the woods and head over to get fed. In a area that had hunting all around it.
If me or one of my buddies who was watching from the house tried it the deer would not come out till we were in the house for a period of time.
I walk my land daily and am out working in the woods for hours on end often.
Many times while working I have had deer walk by within 50 yards of me. They could walk by more than I realize but occasionally I'll stop and look around and see a deer walking past.
I regularly walk by bedded deer that just will lay there an let me walk by, within 30-40 yards.
When driving one of my tractors thru the woods the deer will stand or stay bedded and I can drive by with in 10 yards.
Deer get used to regular activity. After awhile they have no fear of it shows no threat.
Look at how deer behave in cities and suburbs where they are never hunted, they will lay down on the front lawn in the middle of the day in the open.
They have never been threatened in those areas by humans so they have no fear.