Afaik the lightning network currently supports the 15th decimal place...
Cute, but unless
BTC is worth $10 million what does that realistically achieve? Where are you going to spend $0.0000000002?
Apps in Lightning for streaming data, and paying by the minute/3 minutes/5 minutes?
I found
a great answer to the question why Ethereum uses 18 decimal places:
Allowing for 18 decimal places was the only way to move forward. This will allow ethereum to one day achieve it's true market cap and be utilized within our known universe by all species capable of building a computer and communicating through the inter-web to participate in universal-commerce without fear of being scammed.
In all seriousness though, I don't see much point in that many decimals. As far as I know LN "only" uses 11 decimal places (up to millisatoshi), which is already smaller than anything I'll ever care about no matter how mainstream Bitcoin will become.
I sure hope "Pay by the minute" won't reach the point where I have to make a transaction every few minutes, but I also doubt it would be that low if it is going to happen. Why would anyone want to make millions of billing transactions just to earn a fraction of a cent, while uploading videos on Youtube can earn you
up to several cents per view already.
Millisats might not be a feature we need now, or something we can't think that we would need tomorrow, but, it my opinion, it might be a feature that we might be thankful for, and thank the developers, for having the vision.