This is a bad habit.
I know coz I used to do it too, when I don't know about engine braking.
What happens is your mind is trained to always press the clutch first before braking.
Imagine in an emergency brake situation, where reflex is everything. Releasing the clutch first takes away valuable time. Then you don't take advantage of engine braking thus reduces total braking power when you needed it most.
It's the same thing going downhill, or sharp cornering.

My point:
"But when emergency situation arise, people will on reflex do whatever they've always been doing to slow down the car without doing other things.... ".
You just need to press the clutch once while still critically trying to get your car's speed under control and you've lost valuable engine braking power.