I think in some podcast, Nithin mentioned that almost more than 80% of their revenue comes from day traders and F&O traders. They hardly get revenue from long term holders.
This is currently not the case for Groww.
On top of it, Zerodha is totally bootstrapped and have earned a lot of revenue. For Groww to come to that position, it will take some few years and cash burn.
Also, Zerodha applying for AMC license is one step ahead of Groww. If their fund works out, they will be able to make a good amount of money via MF brokerage, without chunking fees for MF managers(as their funds are going to track the indexes).