Why should we usually use insulating tape firstly and heat shrinkable tube secondly to connect and repair cable wire?

When we connect and repair cable wire, if we use the heat shrinkable tube to connect wires, it is easy to have safety problems. If the heat shrink tube is used first, and then the insulation tape is wrapped up, in fact, such a short period of time is no problem, but in the long run the insulation tape may be overheated because of the wire joint, resulting in poor viscosity and will fall off. We may be dangerous if we accidentally touch it.  The correct way is to wrap up several laps with insulating tape , and then seal them with heat shrinkable tubes. This will have a good safeguard. Even if the overheating caused by viscosity is not good, there is no risk of falling off because there is a layer of heat shrink outside.