It can be used to upgrade our monetary infrastructure. You don't even need exposure to Bitcoin if you don't want it. People use it to simply transfer value quickly and efficiently over the internet. Some people find it very useful and so it will always have some value. If it has some value, it can be used for this purpose. It will replace our banking infrastructure like the internet replaced landline phones.

Mining can be used to subsidize energy projects like micro nuclear reactors and solar farms. Stranded energy sources no longer need a residential or business market nearby in order to be profitable. Their buyers can come to them. Imagine setting up towns around stranded energy sources like old gold mining towns. Miners always need the cheapest energy so its really easy for new residents and businesses to outbid them. The miners simply get up and leave for new sources and start the process over again.

It can help bank the unbanked due to its permissionlessness. It gives these people access to more valuable currencies like Bitcoin itself or USD through stablecoins and stable channels.