what's up with the post office

You may not be able to tell this from my blog design, but IRL I'm not very tall. In some parts of the country, I'm definitely shorter than average (i.e., in the Midwest where I grew up). And I never was tall -- I know some people who were tall in 1st or 2nd grade and then lost their advantage. Me, I was always the short kid who read a lot of books and would be publicly humiliated in things like the Presidential Physical Fitness test (where the teacher had to lift me up to the bar we were supposed to chin-up from, since I couldn't jump up that high.)
But now as an adult living in a more diverse part of the country, I rarely encounter situations in which my height is the object of derision or an obstacle to my daily pursuits. Maybe the last time I thought about it was at Target, where the item I wanted was at the back of the top shelf and I had to climb a bit on the lower shelves to get it.
In the past few days, I've had occasion to use the drive-through mailbox at two newish post offices in the city (the parking lot of my neighborhood PO being a pain to negotiate at certain times of day). At both of these branches they've installed super-tall mailboxes aimed I guess at the drivers of SUVs. I drive an 11-year-old little Toyota. The mail slot is actually taller than the roof of my car. Requiring me to stop, put it in park, open my door, get halfway out and mail my letter, feeling like I accidentally shrunk like Alice. What I'd like to know is whether this is now standard at all new post offices, or if they calculate the density of SUVs in a particular area? Or is it the SUV and truck lobby?