I think that the reason why Bitcoin is becoming an asset for people is that it's the only truly decentralized currency with the highest adoption rate and highest market cap, with unknown creator. I'm sure that the fact that single centralized entity can't affect Bitcoin is the reason why it's a store of value but frankly, another reason could be (I'm not sure) that Bitcoin is not the best option for cheap and instant payments.
On-chain speaking, yes, Bitcoin isn't the best option for cheap payments. Fortunately, sidechains and off-chain scaling solutions help solve the problem (like the Lightning Network). It's just that people aren't aware such solutions exist. Even those who know about them express skepticism due to the steep learning curve. UX (user experience) on the Lightning Network is the not the same as ordinary on-chain Bitcoin transactions.
I guess Bitcoin will remain a store of value forever. Still, "the future is not set". So changes/improvements are possible in the long run. You'll be surprised how Bitcoin will evolve in the future. As long as it stays decentralized, there should be nothing to worry about.
