Channel imbalance is inevitable without conscious and active management to prevent it. I used to run an ecommerce platform, and saw the innards of a
lot of merchants. In a nutshell, a winning channel will see snowballing resource investment, and a losing one will be starved. You can force parity, but it usually comes at the cost of overall volume.
Boils down to risk mgmt vs revenue - and all but the most conservative businesses will choose revenue.
In my case, I absolutely starved booking in favour of Airbnb, as Airbnb was much faster out of the gate. So, I have platform risk, but revenue is good.