It is very common among hosting providers to introduce a new cheaper better service without actively reaching out to existing customers about it. Why would they? The older infrastructure is paid for and maintenance on it has a lower cost, and some customers don't want to move anyway because they lack the time to migrate, or don't want to take the outage.
I won't try to answer in general, but in this case? The price is the same so they're getting the same amount of money, there's a good chance the customer isn't running into the 100GB limit any time soon and there's literally no cost to the provider until they do, and if the customer was going to run into the limit naturally the first thing they'd do is see what a higher tier price is and find out about it being free anyway.
That is a common strategy for phone providers too: Keep old customers in old and expensive call rates and compete for new customers with cheaper ones. Providers even store a "sleeper score" in customer data. The higher that score the more may a call center agent spend on one-time incentives to keep a customer in his or her old call rate.
Sometimes, if rarely, these things actually work in your favour. Many years ago, I signed up for a PAYG [pay as you go] mobile tariff with O2 [in UK]. It offered 300 texts and 500mb data for £10/month top-up. The really unusual thing with this tariff though was that, unlike every other tariff I'm aware of, whatever credit you hadn't used at the end of the month carried over to the next month. Usually, with these kind of tariffs, the credit resets every month.
So, as I rarely use the phone for phonecalls I usually have most of that £10 left at the end of every month and it just keeps accumulating. Last time I checked, I had about £260 of credit. Since you can buy Android apps on the Google Play Store and charge them to your phone credit, this means I can effectively get any Android app I want for free. In addition to this, I get a 10% 'reward' back every three months on my top-ups. So, every three months, I get £3 back from 02. I save these up until I've got £10 or £20 of Rewards credit and then exchange it for Amazon vouchers. So, every now and then, I get some free Amazon stuff too.
I'm 100% convinced that some bean counter at O2 made a colossal cock-up, when coming up with this tariff because it was only available for a short time before disappearing and [as I said] I'm not aware of anything like that being offered by anyone else.
O2 keep trying to persuade me to 'upgrade' to a 'better' tariff, which would offer a bit more data and/or texts, in return for my credit disappearing at the end of every month. Er... no thanks. I'll stick with the one I'm on.
I'm actually surprised they haven't [yet!]force moved me to another tariff and cancelled this one.
[Hope no-one from O2 is reading this. Don't want to give them ideas!]
Insurance companies in general and it's also the case in Europe. You often get a better deal just by switching to the current offering even at the same company after a couple of years but they don't tell you.
Things recently changed in the UK with regards to insurance companies:
The biggest shake-up to the insurance industry for decades
takes place on Saturday, when insurers will be banned from
quoting policyholders a higher price to renew their home
or motor insurance than they would offer a new customer.
It can be rationalized. But I'd have been happy to be told they're (optionally) gifting me 10x the resources for the same price if I want it. It actually opened up some backup solutions that I'd been thinking about how to implement from many months. 100GB was not enough. The other options I wasn't sure if I wanted to invest. This hit the right spot.
My ISP replaced their 1000/100 fiber plan with a 1000/400 plan that I didn't get automatically. But it was either the same price or cheaper, so it was merely just a matter of placing an order for the better plan.
That's why it pays to shop around periodically.