FYI even continuous carryover/rollover data had limits. T-mobile capped it at 20 gigs. AT&T uses the same rollover policy as Verizon.
Rollover is a cushion so you can use more of your paid data plan. It’s not a data bank for you to store data for a binge in a future month.
Carriers are careful to manage the network so that it works well for all, when they need it. Continuous rollover data would likely be used during summer vacation time for 80% of users, causing network congestion.
If you need more data for a short term, you can change plans, then change back the following month. Or chose to allow overage, which might be the cheaper option after any rollover is used up