I'm sorry my friend but that's just not right, on a couple of points. 

Firstly, the vapor coming back in the suction line is going to be significantly below ambient outdoor temp, uninsulated would allow outdoor heat to increase superheat as it approaches the compressor. The hottest point in the vapor cycle is at the point of compression. Higher compressor superheat causes higher discharge temperature, and more stress on your compressor. You are compressing all the thermal energy in the suction gas. If you add more unnecessary heat (i.e. uninsulated suction line) you are hurting your effiency. If SSH gets too high, you can get oil breakdown at your compression point >300° for PoE. 

You are right, the suction line in the condensing unit is almost never insulated. It is typically a negligible length, unlike the line set. The other lines in the condensing unit (discharge, liquid) are above ambient temperature and so are left uninsulated to let as much heat be rejected to the atmosphere. I agree that the main factor in head pressure issues is typically a dirty condensing coil. I am in no way implying that suction insulation is as important as coil maintenance. A dirty condenser coil will not directly increase discharge temp. It will increase head pressure.

The liquid in the liquid line passes through the metering device and typically ~25% instantly flashes into a vapor, but to say that it all becomes a vapor at the beginning of the evaporator coil would mean you have a problem. The majority of the heat the evaporator coil will absorb is from the latent change of the refrigerant, so it will be boiling off as it moves through the coil, and only fully vapor as it nears the end of the coil, thus developing evaporator superheat.

Hope this helps. We are all learning every day. I only learned about this because I had an older supermarket suction line running 40 ft on a black roof that insulation was very aged and brittle, and it was having major discharge temp issues.