It's a universal truth of Formula 1 that manufacturers come and go. With the exception of Ferrari, which has competed in every world championship season, other car makers have flitted in and out over the years.
Whether it is current competitors like Mercedes and Renault, or long gone companies like Ford, BMW, Lotus and Toyota, being a member of the grand prix gang or being outside it has been part of the ebb and flow of any company wanting to sell cars. In that context, Honda's announcement that it is leaving at the end of 2021, can be seen as nothing more than simply bringing to a close its fourth era in the championship.
Its latest spell from 2015-'21 comes after competing with its own team in the 1960s (below), as an engine supplier in the 1980s/1990s, and then again as a works effort in the mid-2000s. For a company that is so committed to its motorsport activities, surely it would be logical to think that the benefits of competing in motor racing's top category would make a fifth era inevitable at some point...