Traders post calls for a number of different reasons.
The process of doing so allows them to try out their trading methodolgy in an independent and objective environment (this is actually very important, because the mind constantly plays tricks on you, and many traders will play if I coulda I woulda I shoulda games).
It also allows the trader to prove a given phiosophy, way of thinking, if there has been dialogue on a trading subject and there is some dissention as to its truth of falseness.
If a trader does so and is able to create a consistent track record for themselves, that certainly can give them the confidence/experience they need to put their money where their call is.
Of course if you are a scalper ($50-$75 or less per emini trade) making live calls is going to be a tad difficult using a web based browser, the same can be said if you like to stop and reverse, or if you like to scale into positions.
And like the previous poster said, whether they are making live calls or not, a traders main focus/concern/importance in their trading careers is well, their trading ... thing is, if you're a position trader, you literally have all day, and if you're in a situation where you have alerts for your intra-day trading well, there's going to be a lot (or a little, depending on the day) of waiting around for the bell to ring/light to flash/whatever.
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Ultimtely, no matter what, the trader is going to have to be true to themselves and their accounts, and that fact will not change no matter how many live calls you post. But it will be reflected in your bottom-line.
Good trading (or calling, as the case may be),
Jimmy Jam