[Redrum]

I can't speak for why the public referred to Hillary Clinton as "Hillary",  but it was Clinton's campaign braintrust that chose to bill her as "Hillary" rather than "Clinton". They sure churned out millions of Hillary signs and it might be presumed that it was done to let her stand on her own identity rather than be associated with her husband.  This choice made sense from a personal-identity/branding sense and possibly an assessment that the "Clinton" tag was not entirely positive.  And, though we don't know for a fact its true, it's probably logical to assume that Hillary Clinton had a say in which billing she wanted before the public.

Also, if campaign event coverage is to be believed, those crowds at rallies were not chanting "Clinton...Clinton...Clinton"... the wisdom of the herd chose "Hil-la-ry...Hil-la-ry." 

[Redrum]

I can't speak for why the public referred to Hillary Clinton as "Hillary",  but it was Clinton's campaign braintrust that chose to bill her as "Hillary" rather than "Clinton". They sure churned out millions of Hillary signs and it might be presumed that it was done to let her stand on her own identity rather than be associated with her husband.  This choice made sense from a personal-identity/branding sense and possibly an assessment that the "Clinton" tag was not entirely positive.  And, though we don't know for a fact its true, it's probably logical to assume that Hillary Clinton had a say in which billing she wanted before the public.

Also, if campaign event coverage is to be believed, those crowds at rallies were not chanting "Clinton...Clinton...Clinton"... the wisdom of the herd chose "Hil-la-ry...Hil-la-ry."