Their business model isn't about getting people to use the shared bikes for a small fee. It's about getting people to pay the initial deposit for the right to easily use the bikes. There's room for more than 3 bikeshare companies doing this. By creating an oversupply from funds invested in their capital account, the company can create the illusion of having many bikes available. As soon as someone experiences even a minor problem with finding a bike from their current bikeshare company, they may sign up with and pay the deposit to another company. Although a company in theory puts the deposit into a special account and returns it to the customer on demand, in practise they don't if they go bankrupt and the deposits have already been skimmed.
I experienced this trying to sign up with Mobike as a foreigner in China. After taking a 299 rmb deposit from my bank account, their app presented a screen accepting Chinese citizen ID numbers only. I couldn't find a menu option anywhere for retrieving my deposit money. What is the deposit amount for those bikeshare companies in Seattle?