Soldering makes a metal-metal connection, with the flux ensuring oxides are removed. This makes a very low resistance connection, mechanically it’s very strong, and it’s easy to automate. As a bonus it’s also very easy to undo.

Other technologies like glues and crimping have their uses but are less reliable, higher resistance, or difficult to automate.

This may change but there’s little demand. Glues have lower conductivity and are harder to remove, mechanical connectors are bulky and not as strong.