The numbers you cited say everything that needs to be said. Clinton is unpopular among Independents and wildly unpopular among Republicans. What this means is that she will fail to secure as large a segment of the Independent vote as other candidates could, and that her presence on the ballot could actually drive higher Republican turnout.

So, to answer the question you posed in the title of your piece, first of all because it is 2017 and the next election is not until 2020, secondly Clinton has said repeatedly in interviews that she will not run again, and thirdly, popularity solely among a single-party base in an era where both major parties are losing voter share is not a great selling point.