I wouldn’t say “lots.” It’s mostly just trolls and people looking to stir things up. A very small subset actually believe it’s a scam when looking at Brave as a whole.
Some of it comes from loyalty to Firefox and Google, leading people to criticize the competition. Others just want changes to the UI and think pushing negative narratives will pressure Brave into making adjustments. There are various motivations at play.
Since Brave is open source, anyone who truly wants a lite version can fork the code and build one. But the reality is that no one has stepped up to do it, likely because of the time and resources involved.
Brave itself has considered the idea multiple times. However, as a relatively small development team, they have to prioritize their efforts. More importantly, any project they take on needs to be financially viable.
A while back, Brendan Eich tested the waters to see if people would pay for a lite version. I’m not sure what his final takeaway was, but there didn’t seem to be much interest overall. You can see where I brought this up at Would you pay for simplified version of Brave?
At the end of the day, Brave is a business. They have to focus on sustainability and profitability, not just fulfilling every feature request.