We will look at what's happening imside the oven ??!!
When bread bakes at around 140 degree Celsius, sugars and proteins in flour starts reacting.......
Result : Toasty, nutty caramel smell !!!!
When the sugar in the dough breaks, we get sweet "bakery " smell.
Yeast eats sugar and ejects alcoholic compounds. These compounds smell fruity, boozy and warm.
This also gives " fresh bread " smell.
Warm air coming out of hot bread can travel long to reach our nostrils. Cold bread don't smell.
Our brains are wired to this smell , thinking that food is arrived and it can be eaten !!!