Yes, almost all macaron recipes require a rest time in order to avoid cracked tops, hollow shells, or flat macarons with no feet. The skin on top allows the macaron shells to properly expand in the oven. The air in the meringue gets pushed upward and outward. This is how the macaron feet form. Resting your macarons also helps the exterior shell dry up so the top doesn’t crack in the oven. As the macarons expand, a firm top prevents the moist macaron batter from bubbling up and bursting at the top. If you'd prefer not to rest your macarons, you'll need to search for a no rest macaron recipe that's specifically designed to not require a rest time.