Q:

Why is car A/C typically less reliable than fridges/freezers?

I just had the A/C in my car die on me again; air coming through the vents with the A/C is just as warm with it turned on as off.  However, my fridge/freezer is something I've had for over 5 years and it just keeps trooping on, cooling the food fine.  I've known freezers to last fine for 20+ years.
I presume that both the car A/C and fridges/freezers operate on the same principle of refrigeration, and yet cars seem to need "re-gassing" every few years or the A/C will stop working.  Why is this?  Why can't they make car A/C as reliable as your fridge or freezer's refrigeration?

A:

They are not even close in comparison.
Your refrigerator is a small sealed unit that averages 488 BTU, the compressor speed is controlled to operate efficiently as possible, and is designed to operate in a controlled environment.

According to electricity expert Michael Bluejay, the average
  refrigerator uses 488 BTUs per hour in normal use.

Read more
Your car Air Conditioning is about 5 Tons (60,000 BTU) at highway speeds. Yes sixty-THOUSAND BTU, not a typo. The compressor has to operate at a variety of speeds, from idle to redline, and a wildly wide range of thermal load, and temperature. The entire system has to put up with vibration and movement, and is assembled with lines that bolt or latch together which give many more points for failure. 

A:

It has to do with the type of compressor which is used. The system in a refrigerator/freezer has a completely closed unit, where the compressor is housed inside of the gas. Because of this, all the lines associated with it can be soldered shut with hard lines, etc.  Because of this, a house refer/freezer will not cool as quickly, either. They work very well, but you also have insulation and a lot smaller volume to cool.
A car's compressor is housed outside and the refrigerant pumps through it, with lines which are made of rubber, and seals which deteriorate over time. As long as the seals and hoses remain in good stead, the car's A/C usually will continue running without issue. Lot's of times it's lack of use which causes A/C equipment to go bad. Vehicle A/C units cool a relatively large volume of air (as well as everything in it -- such as seats, dash, glass, etc.) in a very short time. 
We expect much more out of a car's A/C than we do out of a refrigerator. They don't stand up as well because it is made to work and work fast, which has the effect of wearing out faster. If you don't want the car to cool as fast, I'm sure they can make one which will last longer.

A:

Fridge is not a good comparison, it's much smaller than any AC unit. But that's irrelevant, house AC is larger than car AC, yet still delivers fridge-like reliability. 
Both house AC and a fridge compressors are driven by electric motors. They are sealed inside one housing with the compressor with only electric contacts sticking out. This means they are perfectly sealed and coolant cannot leak.
Car AC compressor on the other hand, is driven mechanically by the engine. This means there is a rotating shaft that must enter the compressor housing. There is a seal on this shaft, but it's a moving joint, so it can't be perfect. This is pretty much the only difference between car and a fridge. Due to it, car AC constantly leaks coolant and it has to be refilled every few years, while a fridge sits there for decades with no coolant loss.
And yes, they can make car AC as reliable as house AC. It just has be an electric-driven AC. So in cars that are either fully electric or have a generator big enough (about 5 times larger than usual!), the AC is just as reliable as a fridge. But in a gas-fueled car it's less fuel efficient, as you have to first convert mechanical energy to electricity and then back again to drive the compressor, imparting conversion loses both times. It simply doesn't pay off, it's cheaper to just have it refilled every few years.

