Oh, oops. Looks like they now have a family plan that includes 2 lines and unlimited LTE data for $100/mo now. That's $20/mo less than I've been paying, so I just switched to it.
Damn. Sorry about that, Cricket looked like it may have been a viable option for some people, but... well. Just... sorry. And thanks for prompting me to look into that; it's new since I looked last week.
T-Mobile has actually been running the two unlimited lines for $100 promotion, for a few months now. It's a good deal if it suits your needs and depending on what your state's wireless taxes cost, since taxes and fees are extra. T-Mobile should tell their customers when switching to a newly-released promotional plan would save them a few bucks, but that'd be akin to AT&T lowering your monthly rate if you didn't use your upgrade eligibility. In both cases, the carriers are just hoping a customer's ignorance will continue to fill the coffers.
Again, if you need truly unlimited, Cricket isn't an option. That's still no reason for people who use more modest amounts of data to pay extra for a higher data tier or unlimited plan that they don't actually need. Heck, a big part of the popularity of Ting (a Sprint MVNO run by Tucows) is that it can be extremely inexpensive for very light users.