From a technical perspective, it actually is a bit of a problem.
First, remember that speed is shared with everyone using the same tower (sector) as you. As data usage goes up, that will drop. In a major city where cell density is high it's less of a problem, but it's already an issue in more rural/suburban areas where cells are larger. There are plenty of places in the US that have LTE coverage, but the speed is actually pretty poor.
Second, there are some limit on the number of devices each tower can support. With embedded devices increasingly relying on cellular, we're expecting to hit those limits. So 5G allows for future system growth.
And as for data caps... more available bandwidth does help lower prices. Those prices are, at least in part, set in order to manage system load. More capacity means they can relax the pricing and/or caps.