Why does my bike constantly break/need servicing? I only cycle about 4 miles per day, on roads and paths, which although a little bumpy in places, I'm not off roading.  I'm finding something is breaking or coming loose on my bike after only a couple of weeks or less after servicing it, and I'm having to take it back to the shop every couple of months.
I'd specifically asked for a bike that wouldn't require much maintenance and on questioning the shop I've since been told that ANY bike I bought would be the same, but I just don't really believe them.  People must be able to do 100+ miles without problems regularly surely?
The bike they sold me is a Claud Butler Windermere, which was way lower in price than I was prepared to pay (I was prepared to pay more specifically because I wanted to get something low maintenance that I didn't have to think about).  I also know/knew next to nothing about bikes.
In the 18 months I've had it

Bottom bracket worked loose twice (so it makes a clunking noise), once just 2 weeks after a service
Rear (metal) mud guard cracked through
Chain gaurd cracked through
Pedals loose, broken and replaced with metal ones
Pedal arm thing loose
Rear wheel loose (although they admitted that was their mistake??)
Mud guard bolts dropped out
Handle bars loose 3x
1x puncture
Saddle loose
Gears mis-aligned almost constantly (just make do with what happens to work)
Front break squeals almost constantly (fixed for about a day after service)
One set of rear pads worn, breaks need frequent adjusting, often &quot;stick&quot; on one side.

I have done less than 2000 miles so far, and it hasn't had any impacts - this breaks/cracks have all just come from vibration from riding.
My bike shop has simply told me &quot;no there is nothing they can do in a service to stop these things happening, even the next day, it's just random&quot; and &quot;no you can't buy a bike that is better for any price, so there is no point replacing it&quot;.  I don't have access to many bike shops to shop around.  Are they fibbing?
My ideal would be to be servicing it about twice a year.  Is that just unrealistic?
edit
Just add some details on the roughness of the ride, as I may be a tad rough based on some answers.
I'm about 65kg but also impatient so tend to cycle quite quickly (in a non athletic sense). Top speeds 20-25mph on flatish.
There are three cobbled speed bumps on the route (i do slow down)
There is a short steep hill, which i just keep in highest gear (middle at front, smallest at back) and power through (160m long 12m rise).  I don't really use the front gear.
This is the uk so plenty of rain.
At home it lives in the garage. During day in a covered bike rack.
Edit
Just to add closure to this in case anyone is interested as it has been a few years now.  I followed the advice and switched bike shop AND bought a new bike - more expensive Raleigh Strada 5.  Totally different experience with this bike and shop - reliable and no comparable problems.  The new bike shop gave the old bike a good going over and it is now my back up bike - it is clearly nothing like the same quality as the new bike, but none of the alarming problems since switching shops.  It does go to show that even as just a commuter rather than a bike enthusiast, there can still be a big difference paying a little bit more.
The bike you have is a decent low/mid-range hybrid bike with entry-level name-brand components. It should absolutely be mostly trouble-free with basic maintenance for a daily 4 mile commute. While replacing the cheap plastic pedals with a decent set of metal or high-quality poly pedals is standard business for any new bike, the other problems are worrying. 

To be honest I don't think it was assembled correctly at the shop, and the mistakes in assembly - mis-alignment of the derailers, improper torquing of components (too loose for the bottom bracket and crank, too tight for the chaincase), etc. - are causing new issues to pop up on the regular. If you bought the bike from the shop who's been fixing it, find another shop. Heck, find another shop, period - any pro bike mechanic worth their salt should be finding and fixing these issues on their work-stand before you find them on the road. 

It may be that there are so many problems on the bicycle that need remediation, a new or gently used bike might be a more economical solution than trying to bring this one into some semblance of repair. Find a different shop to buy it at and to maintain it.