A. A solder joint tends to deteriorate over time, and become electrically and mechanically faulty. Moisture, for example, causes corrosion of the metals. The lead and tin in solder also tend to oxidize over time.
Soldering is also awkward and slow compared to crimp connections and wire nuts. A connection on a screw terminal is also better if it is made to the wire itself or if a terminal is fastened to the end of the wire for it.
Also, some electrical wire is aluminum, which requires a special solder and a corrosive flux.