These are half-truths.
Yes, recording MIDI cvan be used to trigger soft synths on a DAW. However, you aren't limited to that. You can also trigger the same synth you recorded the MIDI from.
I often record the midi out of my synths, but still playback the sounds from that synth via MIDI.
How it works (read the link above) is that you store the MIDI information (which is essentially instructions as to what note note to play on what patch when, how loud, and for how long) on your DAW. In other words, you grab the performance information rather than the audio itself.
When you play back the MIDI stream, it triggers the sounds on the synth. In fact, anything that understands MIDI can be triggered.
What this buys me is editablility. Once I record audio, I am limited in the editing I do. However, when I record the MIDI information of the performance, I can readily edit the notes, change the patch (sound), synth/module, change keys, whatever. When I'm happy with it, then I freeze the track (record MIDI to the audio).