Why do many clipless pedals use bushings in addition to bearings?

Loose bearing-only systems have been used with hubs and bottom brackets, so why not clipless pedals?

Is it because clipless pedals are so small in size, so additional bearing contact surface area is desirable?

Are all pedals like this?

Relatedly, do any clipless pedals have especially simple internals (or access to internals)? I've heard that Time pedals are easy to service, but I haven't seen any official documentation on the subject.

I think the idea with a lot of clipless, especially the cheaper stuff, is that they have a lifetime (say, 5 years) where they go great, then suddenly wear out. They don't need to be user-servicable because they are so cheap to replace.

I haven't seen any with bushings. I have worked on shimano, Look, Sampson and a bunch of cheapies, but none with bushings. It is good enough for our application. Our loads are not that high and the rpms are low.

I may be wrong about the existence of bushings in most clipless pedals, but the disassembly instructions for Crank Brothers Eggbeaters certainly mentions bushings. And the exploded views of Shimano M520 and M540 pedals look like they contain bushings (the two cylindrical parts between the ball bearings); the same seems to be true of Time Alium pedals as well as their other models.

Perhaps 'bushings' isn't the correct term, but they do seem to be a moving part of the bearing assembly. Speedplay and Bebop pedals don't seem to use such things.

Jimbob, I don't doubt that some pedals are intended to be disposable; I just wish it weren't so.

**I should have mentioned that I'm looking exclusively at mountain pedals.

The shimano cyclinder in the sketch is the ball bearing housing. It comes out as an assembly. To grease the bearing you remove the assembly, clean the housing, pack it with grease, and screw the axle assembly back it forcing grease out through the bearing.

I didn't really mean 'disposable'; just that most products nowadays are designed to have a predetermined lifetime, and are correspondingly designed with or without servicing/maintenance in mind.

I entirely agree that it's a pain a lot of the time though; I'd much rather pay a little more for something I can trust to last the lifetime of my bike, rather than have to think about replacement.