In case of a manufaturing company or a capital intentise company I think an onsite visit is very helpful to have a look at the facilities, check the type of assets they have, the culture and environment of the site and the people and their attitudes and informal language.
In the case of retialers, it si very important to visit the most relevant shops or slleing points they have. Even through mistery shoping. Talk to customers, employees, look at the organization of the shops, check the products, see what cusotmers buy…..
In case of financial companies is probably less relevat since you are buying a loan portfolio and financial assets and may have online services, but it is relevant to visit the most important branch offices and see the operations.
I would imagine, in certain industries, on-site visits are very important during the Due Diligence. In my experience, I found on-site visit most helpful during the assessment period, before the offer is even put across. You can see and understand a lot about the target when you visit them, especially softer factors, such as company culture, management competence and market knowledge etc. You are sometimes able to glimpse the facts behind the well-polished CIMs.
I believe there is a lot of value in an on-site visit. You can first hand observe the status of affairs and feel the overall vibe and culture of the place. If this comes very different than what you were expecting or does not flow what you have read in the papers from data room then that should already raise some concerns. Further getting the opportunity to talk to people gives us the opportunity to assess the competence and compatibility of the target organization.