This might be an obvious explanation, but sometimes you just need to get somewhere now. If this is your first time in Peru, you probably want to see as much as you possibly can. You may not get a second chance!
Flying allows you to go from the coast to the mountains to the jungle in a single day, realistically giving you a chance to see it all in less than a week.
So, for your next trip, get creative and explore your options. Sometimes, when you travel by bus in Peru, you find some of the country’s best hidden gems. But if it all seems too daunting, get to the airport.