It was this exact question that lead me down the rabbit hole to making espresso machines. The main reason everyone uses them is because they're $25, small, and can leverage the oscillation of mains voltage for their operation. The next best thing is probably $300 and quite large and heavy - and those professional gear pumps fundamentally don't scale down well. Ours operates under the same principle though with a completely different sort of motor that hasn't been common until pretty recently.