Every house in my subdivision has the water heater in the attic. It's a Lenar subdivision.
Not only that, but the plumbing contractor they used, I found out, used old stock for everything. Must have found a warehouse of unsold plumbing equipment and bought it cheap.
My house was built in 2000. The manufacture date on the original heater was 1996. They also used outdated and no-longer-manufactured polybutylene for the run from the meter to the outside valve, so a bunch of us have had to have that garbage replaced.
I got estimates for moving the water heater to the garage, but it'll just be cheaper in the long run for me to keep replacing water heaters earlier than actually needed than to have the move done. I got a new pan and one of those alarms, and I make sure the batteries are good in the alarm by replacing them when I do my air filters.
I have one of those as well. Ran a power cord to it, not going to worry about batteries and get bit by forgetting. But they do work, they broke the seal on the exhaust stack and the roof leaked into the pan and shut that water right off.