This is likely due to average height and common usage.
Ada toilet grab bars location.
Side wall rear wall rear wall the rear wall grab bar shall be 36 inches 915 mm long minimum and extend from the centerline of the water.
Grab bars located behind the water closet shall be at least 36 inches 915 mm in length.
Typically grab bars in the shower should be installed 33 to 36 inches from the floor of the bathroom this is according to ada americans with disabilities act standards.
A 42 inches 1065 mm minimum length grab bar is required on the side wall spaced a maximum of 12 inches 305 mm from the back wall and extending a minimum of 54 inches 1370 mm from the back wall at a height of 33 36 inches 840 915 mm.
One end of the grab bar is shown near the corner of the stall closest to the water closet.
A side wall grab bar complying with 604 5 1 shall be provided and shall be located on the wall closest to the water closet.
Grab bars are required in accessible toilet rooms.
In order to comply with the specifications reach range the toilet must be centered 18 to an adjacent side wall or partition.
The toilet paper dispenser shall be mounted below the grab bar at a minimum height of 19 inches 485 mm.
Are not automatic they must be located on the wide open side of the.
However you will often see them while in a toilet room or in the accessible stall.
Grab bars shall comply with 609.
They can be located below or above but not behind grab bars though it is important that non recessed dispensers be outside the 12 minimum high clearance above the bar yet not exceed the 48 maximum height measured to the outlet of the dispenser.
Grab bars location typical toilet water closet not in a stall.
The ada says that grab bars should be installed horizontally between 33 inches and 36 inches maximum above the finished floor to the top of the gripping surface section 609 4.
The ada standards require horizontal grab bars on the rear wall and side wall of the water closet but it does not specify a vertical grab bar.
Two grab bars shall be installed on the back wall one located in accordance with 609 4 and the other located 8 inches 205 mm minimum and 10 inches 255 mm maximum above the rim of the bathtub.
Figure 30 a shows this end 6 inches 150 mm maximum from the corner.
The sidewall must be a minimum length of 54.
But i would strongly recommend to take into consideration the height and physical capabilities of the person you are installing these grab bars for.
In addition a rear wall grab bar complying with 604 5 2 shall be provided.
Each grab bar shall be installed 15 inches 380 mm maximum from the head end wall and 12 inches 305 mm maximum from the control end wall.
All grab bars shall be located 33 36 inches 840 915 mm above the finish floor.