The short answer
Nithin Kamath states it as a freedom rather than a sacrifice: it is a good place to be when you do not have to look at customers in terms of acquisition cost and lifetime value, because then nothing forces you to push people into trading or to sell products that suit you rather than them. It began as a constraint, since Zerodha had no money to advertise at launch, and it survived on purpose: referral incentives started in 2010, changed repeatedly with regulation, were disallowed around 2018 and 2019, and today there are none at all, yet referrals stayed roughly flat. Sridhar Vembu makes the same argument from the product side, that venture capital forces you to grow faster by spending on sales and marketing instead of R&D, and if you do not invest enough in R&D you will not have long term growth. Zoho crossed a billion dollars in revenue profitably, and Mani Vembu confirms the spend on R&D is still a lot more than the spend on marketing.