They also tend to pester you for food or walks roughly at the same times every day, so, no matter how irregular your lifestyle was, there suddenly is a wireless alarm clock all day. Every single day. (Kids are much better at this, though).
In the EU and US at least, you can get this all for free: Sign up as a volunteer at the next animal shelter, commit to walking one of their dogs twice a day, 7 days a week :)