Because you already spent 25 seconds waiting for the phone to ring (for which cellular providers charge, but not land line long distance providers), plus 7 listening to the greeting that the user recorded.

There are still carriers that charge $100 per year extra for a call log. And these carriers still have customers.

Have you tried sending a text on a flip phone? Or a land line?

And you end up waiting for hours for someone to get to a desk to compose and send the email.

That's because a proper captive portal will MITM not only every DNS request on port 53 but also every HTTP request on port 80, no matter to what IP address, and block connections to unapproved IP addresses on all other ports. So even if your machine produces no outgoing packets on TCP or UDP port 53, the captive portal still grabs you when your machine opens a connection on port 80.

Not all cellular devices and plans support e-mail or IM, and sending a text from a flip phone is painful even with T9.

Not everybody pays for a $500 per year smartphone plan. For example, sometimes it might be hours before I can get to an open Wi-Fi connection through which to send an e-mail from my laptop, but I can leave a voice mail from my $80/year flip phone. What would be the most polite way for someone like me to call you?

That's probably because they're calling you on a pay-per-minute line and want to finish their message as fast as they reasonably can in order not to be billed for a second minute. Land line providers charge extra for long distance. Cell phones have free long distance, but less expensive plans charge per minute for airtime. Finally, international calls are expensive on pretty much any popular provider. This is made even worse by the lengthy instructions that many carriers append to the greeeting: "At the tone, please record your message. When you're finished recording, you may hang up or press 1 for more options. To leave a callback number, press 5."

Pay as you go plans are like that. Or try Ting, a Sprint MVNO operated by Tucows that separates talk, text, and data billing into three independent bins. But good luck sending text messages to or from a land line.

A lot of people who rely on voice mail don't pay the extra $8 per month for Caller ID.

"Hello?"

"Hi, this is Staisy, What's going on?"
"I explained everything in the voice mail I left."

What's the polite way to continue?

Then what do people put in for the "Recovery e-mail address" when signing up for other-than-ISP-provided e-mail?

Do people likewise complain when they can't get to "financial institutions and e-commerce sites" on the local public library's Wi-Fi without first logging into the hotspot?

That'd be true if DNS poisoning is the only layer that a provider uses to corral users into their captive portal. But based on my own experience with captive portals, that's rarely the case. Say you have 123.45.67.89 www.example.com in your hosts file. Any HTTPS connection to 123.45.67.89:443 will produce either "Connection refused" or a certificate error. Any HTTP connection to 123.45.67.89:80 will produce a Location: redirect to the page for expressing filtering preferences.

You'd be able to access your ISP's mail and its billing department. Everything else, such as third-party webmail and POP3 or IMAP connections, would be hijacked or blocked until the householder expresses a filtering preference.

To save on costs of fielding telephone calls from people who can't get through to any web site because they don't know where to go to express a filtering preference, and everything but expressing a filtering preference is blocked.

Good luck. The modem rewrites the MAC on the way out as part of its data link duty, and either the modem or the ISP-owned router on the other side of it drops outbound packets that don't have the subscriber's IP address in the from field.

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The ISP can just drop all packets to the Internet on port 443 until the householder has confirmed his censoring preference.