Okay, "supposed" to means you know (and I know) they don't always do it. Also phone and cable companies sell wireless equipment to their consumer and they will install it. It's a matter of revenue, which means they should secure it.
You are assuming everyone knows that a wireless signal is inherently insecure. That's not the case; you know it and I know it. Now what if someone shares (I've seen it) sensitive data. Are you allowed to just take it and do anything with it? What if you have the same cordless phones, and yours connects to their system? Are you allowed to make calls whenever because they failed to realize you were using it? Where do you draw the line?
Most people don't understand the need to apply OS patches either. Does that mean you can just break into their computers because they failed to do so? Absolutely not.
The fact is someone is paying for a service for their use, not yours. This is third time I've said it, but I'll say it again, because you choose to ignore it. You know it's not there for you to use, so you should either help them out or stay off the network.
EDIT:
You added this:
No I won't cut it out. These services cost money, and you're not paying for it, so you are in the wrong. I work hard to buy things for my family, and petty thieves such as this need to be called out. I'm not working to pay for someone else to have Internet access.