sharing homemade pics and videos that include nakedness or even controversial things are not best done via the big tech centralized solutions. Same with sharing non-homemade videos or music.
Other use cases come to mind for sensitive business comms and others.
I did not watch the video you mentioned about how it works - but scanning a few pages about the product I did not see anything about end-to-end encryption - so this product seems to not check off the needed boxes to do well what I think the use cases could be.
I also checked the pricing and feel that it does not lend itself to my trust cases either - free is nice but no skin in the game for sensitive things? I also generally do not invest in monthly/yearly pricing schemes - I like an option to buy once and use version X forever with self hosting options. So my initial curiosity about the title and considering use cases is left with disappointment - although I do think something similar could be made and sold.
Interestingly "bitwarden' is also currently in the top couple pages of HN and it sounds similar, but looking into it - it's not.. but it does mention E2E - and mentions a self hosted option - although my initial poking around makes me think it's not for files just a passwd manager.
So that's 0 for 2 for me today, thinking by looking at the headlines someone may have created a friends only auth / E2E dbox / Firefox send replacement.
Use cases exist, and the big name options are not as private as many would like / use. I know reasons.. but still one can hope :)