All those other planes you've mentioned are twins, and so need to be able to start the APU to satisfy the engine-out rules when over water.
The 747 is a four engine aeroplane and so is rightly considered to be quite safe from losing all four engines. Yes, it has happened before a couple of times but when you consider the number of flights that they do it's extremely rare indeed.
That's also why they don't have a RAT, they don't need one. But in the unlikely event that all four fail they will windmill over fast enough to provide enough hydraulic pressure to make the controls work. The battery will probably run for about twenty minutes os so, maybe longer, but if you haven't got the engines going again after that length of time you probably never will and so it's not going to be important any more.
FWIW, I'm a 747 Classic driver not a -400 driver, but the principles are the same. Having four engines allows you far greater flexiliblity as to where you can go with restriction.