You are assuming that the only people he wishes to promote himself to are the wider public.
Simple example - in my own field, senior officials who still have a lot of power but who are of a different generation, view people who are on twitter, or who blog, appear regularly on TV etc as 'lightweight', 'not serious' and 'not credible'. People are advised that if they want to set the right impression then they should get off twitter etc.
Now, you can get off twitter as a way of self-promoting yourself to those who are potentially suspicious of twitter etc but hold the levers of power and demonstrating that you are 'serious' and not a 'dilettante'. Some people (I'm assuming in this case not Millar) have very ostentatious twitter 'retirements'.
The public won't be voting for Millar for UCI President, but the blazers at the nationals feds will.