At the time, that was the best compromise of low power, unit size and cost. Even Windows had a 32 bit win8.1. Many of those devices have 32 bit UEFI and there a lots of them just about ready for a second life with linux. Many can run 64 bit distros, but not usually OOTB. But a 32 bit OS gets more out of the meager 1 or 2 GB RAM, by almost 25% on my device.