Taste can definitely be influenced by temperature. It's easy to experiment. Cook something, eat half of it at the intended temperature, then chill the rest and eat that. Notice the difference.
Then repeat that with a dish that doesn't require heating. Eat half of it cold, then heat the rest and eat that. Notice the difference.
Which of these flavours you prefer is probably in part cultural, part personal preference.
If you mean why we started heating our food in the first place, it's largely to do with food hygiene. Cooking meat and plant material kills a lot of the harmful bacteria in it, meaning you're less likely to come down with food poisoning.
Freezing has a similar effect, but is far harder to achieve in most climates in a pre-technological society (even in Europe for example, ice was a very expensive luxury in summer until around the 1940s and the advent of electrical freezers. The only ice people had was what was stored in underground ice cellars during winter after being hacked out of rivers and lakes, and slowly melted during the year.
Another reason, one probably discovered by accident in many cases, is that some plants (and probably animals) that are poisonous/toxic before cooking can be safely consumed if heated to a high enough temperature for long enough. This increases the selection of available nutrition, which can be very important for survival as groups grow in size.