It’s crystal clear: considering that leads convert to customers, and customers can either be persons or companies, ERPNext cannot just provide us with first and last names for leads, because that would fit conversions to individual customers well, but not companies. Companies have no first and last name.
However this gives me trouble in lead management, because I don’t know how to automate written communications with leads: I don’t want write “Dear {{ doc.full_name }} …” and similar, I need a first name.
The question is: did anybody have this issue? How did you solve it? Is it possible to add a checkbox to distinguish individual leads from company leads? So when you check it you can fill in first and last name, otherwise you only get full_name. Accordingly, leads would convert to individual or company customers.
Hints?
What version are you on? On Lead, now there are 2 separate fields Person Name and Organization Name. I guess this should solve your issue, right?
Oh boy, you are so right 
I kept checking an old version 
This does solve it indeed, many thanks!
Sorry, @KanchanChauhan too fast. It actually improves the workflow, but still the issue is there, because you won’t make separation between first and last name. Actually when you convert a lead you end up attaching a contact with person’s name as first name.
You still need to either forget about the last name in Leads, and add it manually to contact once it converts, or save the full name as person’s name, thus persisting the problem in addressing the lead successfully with automated communications, and manually having to modify the contact later, to break up person’s name in first and last.
I think the point arises because you literally trying to convert a Lead to a Customer, which actually is not correct as I explain here.
By “converting” a customer you actually “convince” somebody, you do not “operate” on a company/customer. In fact it usually happens that when the “converted” person leaves the company, the company looks around to change suppliers as well.