You don't buy bits 1 for 1. You pay a premium for bits. if someone spends $100 on bits and sends them all to someone, you don't get $100 in bits.

The default ratio is $1.40 for 100 bits.

And the 50/50 split for subs is only on the web. In the app, it's not a 50/50 split as the subs cost more.

Yes, the streamer gets 100% of the bits, but it's not equal to the $$ amount.