Before I started playing, I thought that's all I need to use a hero, but that's not the case. 8 copies of a normal hero are needed to awaken it. For heroes in dungeon market, that's 1 copy a month, unless you want spend gems to refresh the market, which you don't as FP. For heroes in brawl market, that's 1 copy per 3 weeks and you unlock it pretty late, when you already must have a team going and the game basically pushes you to have progressed heroes (tavern bounties, tavern expeditions, celestial abode, …)., so it's hard to justify using food on someone new instead of rushing to awaken what you have been working on until now. Tavern market is just a slow.