Resolved Question: why is it necessary for so many Wills to need probate and why does it take so long?

I understand that it is all about people’s assets including property. But most ordinary people own property because they had to buy a place for somewhere to live not because they are affluent. I have heard that Probate can be done without the help of a Solicitor, and if so it can be dealt with quickly. How? What is the difference apart from paying out massive solicitors fees compared to a pittance for do it yourself.