Xfinity Mobile: What's Missing?

We have reviewed each page of their web site, read all the disclosures and added up their plans.  We just don't see how Xfinity Mobile can save us money.  The terms say nothing about free Wi-Fi, therefore, you should be charged whether or not your phone is using Wi-Fi or the Verizon Wireless network.  Since you must be a Xfinity Internet customer, you are already being charged for Data.  If you were not an Xfinity Mobile customer, and using any other cellular carrier (or an inactive smartphone), your Wi-Fi data would be Free...right?

Let's say we're wrong about that.  Let's also consider that you can't bring your own phone, you can be "throttled" (after 20GB) on Wi-Fi and all voice calls are completed on Verizon Wireless. What's the point?  We weren't going to give Xfinity Mobile a Mountain Wireless Rating until it had been field tested by fellow users.  Other "Wi-Fi first" services aren't as reliable as cellular-first carriers, but we thought we'd give Xfinity the benefit of the doubt.

Related: Do They Have Their Own Network?

If what we read is true (and we'll allow that someone made a big mistake when writing the rules), we're hard pressed to even give them a "2" rating, the second lowest.  Xfinity Mobile charges $65 for their Unlimited plan ($45 promotional price during July).  But if I spent $45 for Straight Talk Wireless, I would get access to "Unlimited" Data (throttled after 8GB) on the Verizon Wireless network, be able to bring my own phone and use my Xfinity Wi-Fi for FREE.  What's missing?  A clue: One of their web pages says, "With access to 16 million XFINITY WiFi hotspots, you can do what you love on your phone without adding to your 4G LTE data usage."  Does this mean Wi-Fi is Free?  No.  We'd ask but Customer Service is closed right now.