Clinton had to abruptly leave the fifteenth anniversary of the tragedy of 9/11 at Ground Zero, claiming she "overheated". She apparently collapsed and had to be dragged into a waiting van by a phalanx of bodyguards.
We have to seriously ask ourselves if Clinton is physically capable of serving out her duties as president. Some people might counter that FDR served three and a half terms from a wheel chair. That's true, but his mind was unaffected by his paraplegia. FDR could not walk, but he had tremendous stamina. Clinton is very clearly unwell. Her health appears to be deteriorating rapidly.
This has nothing to do with policy. If Trump was falling down, or had frequent coughing fits, or needed aides to climb steps or get out of cars, I would question his ability to serve as president. The American people have a right to know about the health of their prospective leaders.