Keir Keir Starmer's associates, Rachel Reeves and Wes Streeting have deliberately alienated some Labour voters though, by saying that they are glad that those who supported the policies of Jeremy Corbyn and John McDonnell have left the party.
Keir Starmer was elected as leader on a left wing manifesto and on ten pledges that he made which he has not kept to.
So maybe one answer to the question posed in the OP, is because he only wants the votes of Conservatives or small "c" conservatives.
I notice that Labour are now saying that they will introduce a national social care policy. This is a very good idea which was in the previous manifesto. It is not a new idea that Keir Starmer should take credit for.
How can we thank the Fire Service?
Just got congratulated for being able to use my debit card!

