It's no big secret that a lot of people are lazy. There's nothing really wrong with that as long as you're not sponging off of everyone else. If you're doing what society requires of you, but little else, you probably want to make sure that the rest of the world gets that. Wearing your message on your clothes can help you get that across faster, and you won't have to waste the energy to explain it to other people. Just saying you want to boycott Mondays or that you're an unemployed English major doesn't really hold as much interest for others as proudly displaying it across your chest. Advertise, and fellow lazy people will find you…assuming they have the energy.
Lazy shirt at SnorgTees