There's no reason to divulge earnings, merely that the person does really trade a live account. Most people do not have multiple phone lines. Phone verification is popular and common, to reduce multiple nicks.
ET isn't a massive space like Twitter or Instagram, additional verification would likely mean fewer users registering. There's also some additional costs for Baron associated with this.
What does a live account verification achieve. Not against this idea but if someone has a $2k account and places 3 trades a year, it doesn't change a thing. I suppose people who want could show account balances and while very crude, the range of that number could be in the profile.