SimonM wrote:I always thought it was to do with current.
As the voltage goes down (1.5v down to 1.2V), current goes up and hence damages sensitive electronic equipment.
Typically the current will go down if the voltage goes down. No risk of damage to equipment unless the designer pretty much goes out of their way to make it otherwise. It is possible with a voltage regulator to increase current as the voltage drops and this would result in constant power draw as you describe, but then the regulator would provide stability so no risk of damage.
In any case, as an alkaline battery gets exhausted, its voltage drops to zero (if connected to equipment that's on). So all battery powered equipment has to deal with the voltage dropping anyway.
The only reason to "require" alkaline batteries is that it reduces the number of people complaining about power related issues. For example, the "battery low" alert will be accurate (instead of getting 30 seconds warning as you might with rechargeables when the electronics is designed to predict remaining battery life using the alkaline discharge curve), you'll get the advertised battery life, and when any battery runs low the equipment will start to malfunction (requiring a reset).
There are other complex differences (eg. internal resistance) but this rarely makes a difference.