Security at its western borders, a major trading partner. There are other things.
Its western borders aren't threatened - France is not going to pick a fight with Germany on its own (and France getting allies like it got Russia OTL is something that can be dealt with in regards to dealing with those powers) - and it can have France as a trading partner without committing to a full out alliance.
Some of the others:
British sea blockade will be much more difficult when they also have to cover the Gulf of Biscay and French Mediterranean.
And so what? What war is Germany planning that involves opposing Britain?
The Low Countries will probably be at least friendly neutrals.
Can be done without a French alliance.
French colonies diverting more ressources away from the european theatre should a major conflict arise... I guess the UK might refrain from an amphibious assault and concentrate on colonial warfare, leaving the land war in Europe to Russia (and Austria-Hungary)
This just isn't the sort of thing that lines up with German interests. Germany wants one of (to put a bunch of complicated and competing plans that were OTL handled in a sloppy way into neat categories for alt-historical purposes) two things - "a place in the sun" as far as the colonial and global game goes, where a friendly Britain is more valuable than a friendly France, or European dominance (not necessarily control, just being #1) - where France is a rival, not an ally.
This just looks to me like an alliance of Red Player, White Player, and Green Player against Blue Player, Purple Player, Orange Player, and Pink Player. Which is to say, it has no relationship to the interests or attitudes of the powers involved, it just shuffles around countries between alliance blocs.