First, there are situations where it's hard to get "awesome LTE" because there's a lot of usage. Getting more bandwidth is important to handle situations like that.
Beyond that, we don't know what the future will offer if we build greater capacity. When Apple launched the iPhone, we didn't know that we'd be changing the way we live our lives. Things like TikTok wouldn't exist without the abundant bandwidth offered by LTE. We don't always know what greater bandwidth and capacity will offer.
We are seeing some things already. We're seeing wireless home internet become available to a lot of people. For cell carriers, this is a new stream of revenue. For customers, this can be increase home broadband competition and for many rural customers the first chance at broadband.
We're seeing things like Nvidia's GeForce NOW allow you to play games that are being run on the cloud rather than your local device. Lower latency and greater bandwidth/capacity means a better experience. Nvidia recommends 50Mbps which LTE can do, but won't have as much capacity to support as many simultaneous users. 5G will also drive down latencies which are important for gaming.
It's possible that self-driving technology might take advantage of this in the future. I'm not someone that promotes self-driving tech, but one can see how lower latency and higher bandwidth/capacity could mean being able to send more data to the cloud both for computation and also for storage/learning.
A lot of people are talking about VR and meta-verses. Again, I'm not necessarily buying into this yet, but it seems like greater bandwidth and lower latency could make things better.
Heck, even video-conferencing on mobile can benefit from more bandwidth and lower latency. While LTE can accommodate it, there are times when networks get congested and less congestion is a good thing. Lower latency also offers a better experience.
Do you need it? No. But you don't need a smartphone. At the same time, it's possible that someone will create something that you won't know how you lived without that's made possible by more bandwidth/capacity and lower latency.