There are lots of reasons to send a track to two busses or outputs: Key inputs, parallel processing, alternative track prints, the possibilities are endless. Its very common to find people using a send in combination with the main channel output to mult the output. This is the right way to go if you want to send different amounts to each destination. I've even come across people who duplicate the track and send each version to a different destination - wasteful but effective.
If you are going to leave the send at unity you might as well just mult the main channel output using Ctrl/Start. Simply hold the modifier while selecting another output or bus. A "+" in front of the output shows that multiple outputs are selected. I use this all the time. Try it!