You may have heard mention of limiting the amount of food that you take in while riding to 200-250 cal/hour (or in that range - it varies based on who you are and how hard you are riding). Because that's considerably less than the amount you are expending (in many cases - if you are riding slowly and are quite fit, you may be able to take in enough food to meet your needs), even if you are getting carbs/protein from food during the ride, you will be typically finish your ride with depleted glycogen stores and low blood sugar.

Right after exercise, your body is better at absorbing and using carbohydrates and protein - that's the whole purpose of recovery nutrition. This degrades over time, and after perhaps 2 hours or so you're getting back to your normal absorption rate.

If you don't get adequate recovery carbs/protein, your body will tear down your muscle tissue to get carbs to replenish your muscle glycogen. This will make your muscles hurt more and reduce any strength gains you might have made.

While you exercise, you also get appetite suppression. This lasts for a litle while after you exercise (about 30 minutes for me), and if you can get some recovery food, you can get your blood sugar up and avoid that "eat everything in sight" syndrome. If you are riding to lose weight, that can be important.

Now, the matter of what to eat. All the research I've read says that real food is just as good as recovery drinks. My experience is that recovery drinks have some real advantages. First, they are quick to prepare and consistent from time to time. Second, because they are liquid, they are absorbed faster than solid food (you don't have to wait for them to break down). The obvious disadvantage is price, and the fact that you have to remember to bring them with you.

I've tried doing recovery with plain food. It may be that I'm not getting the right food, or it may be that my timing is too late (I sometimes drive home after a ride and don't get home until at least 30 minutes after I'm done), or it may be something else, but I would often feel like I was missing something. Since starting on Endurox, I don't get that any more, and it seems to have a significant impact both on how sore my legs are and how much energy I have later in the day.

Whether you need to worry about recovery depends on how you ride. Very generally, if you are a trained rider riding at moderate rates and eating along the way, you may be getting the majority of your energy from fat and the food you take in may be enough to keep your blood sugar up. Or, if you are only riding for an hour it's probably not an issue. On the other hand, if you are riding 2 hours or more, don't get many calories during your ride, or are riding at a speed that burns more carbs, or if you are training multiple days in a row, recovery nutrition can make a significant difference.

Food for fitness (Carmichael) is a decent reference on food and training in general.