The fallback language for Fula (ff) is French. This means that things that are not translated into Fula are shown in French, rather than English. This was done in 2007 after a request from the user Kasper Souren: T13266. I don't think that it was discussed much more than that.
Fula is spoken in some countries where French is official, but it's also spoken in countries like Nigeria, Gambia, and others, where English is official. I've also checked the statistics about countries in which the Fula Wikipedia; out of the top 20 countries there, the only French-speaking country is France, but it accounts for only 2% of the pageviews.
Therefore, I'm not sure that it's good to show French to everyone.
This was also discussed at https://ff.wikipedia.org/wiki/Wikipedia:Damugal_renndo#French_fallback