I think so called expert traders that claim to be such, actually hide what they really invest. They pretend to go in with more than they actually do sometimes. That's so easy to fake actually that its ridiculous.We shouldn't accept anything less than DEX blockchain transactions from a signed address as proof of trades and profits.
There are some things that are actually necessary otherwise they might not gain the attention of their target. There is no perfect person, and I think that it will be impossible for any trader to actually make trades without having any loss even if the person is the best traders in the world, but because of the lack of understanding of people for this is the reason why some people hide their losses.
People expect that some trader will be perfect and not have history of losses, and I think that it is unrealistic of them to think so, and they might judge the person based on that and never patronize them if they know they are making losses, so that is the simple reason why they hide it, but if it was me, I would not do that because I can as well start trading for myself alone and be making money if people are not willing to put their money down for me.