Why don't we budget time?

It seems like everything I read about personal finances, one of the first things people recommend is having a budget. Except those that don't like the word "budget" they say have a spending plan. But the idea is always the same - plan what you are going to spend, and then follow the plan.

Pretty much the same goes with eating healthy. People plan what they are going to eat and then follow the plan. Examples include Weight Watchers (points system), Paleo (don't eat junk), and things like Nutrisystem (buy our food and eat that).

The one thing that people seem to not really think about budgeting is time. There are scads of methods of doing todo lists, project planning, prioritizing etc, etc. But very little similar to what I would consider a time budget.

Let's do a comparison. If you go out and spend money, you eventually run out of cash, overdraw your checking account, or hit your credit limit. You know when you have run out. You can do the envelope system or follow a budget and keep from going that far if you track your spending and stop before you hit your limit on any category.

Time: it is often that you can start on email, Facebook, Twitter, or maybe looking at cute cat pictures on Reddit and next thing you know what in the world it is 3AM, you meant to go to bed by 10:30 PM because you have to get up at 6AM the next day to go to work.

Very few people I have heard of do a time budget. In the above example - maybe at 10PM you could set a limit of 30 minutes to goof off on the Internet before going to sleep.

Is it hard? Or is it just something no one thinks about that often?