No it doesn't need one
But should be supplied with one so the customer has the option to use it or not..
Only my opinion..
I know the ones supplied are really poor, so do the customers. But it's just one of those security things that they like. Just in case they forgot the pencil case init..(the one with the rubber in init..)
I know someone who bins the pen and kit once the first lead and rubber is worn out..
I have now managed to get his secretary to return them for a refurb. New rubber and re fit with new lead for a fraction of the price.
As for 0.5 or 0.7. It's all down to what they prefer. Mine have always been 0.5.