Deity benefits

[Akzeal]

Is there any benefit to having a deities if you are not a divine caster

[VRMH]

Yes, some spells benefit you only (or more) when you share the religion of the caster.
And there's the roleplaying boon of being part of a larger group of people.

[zend0g]

And you have the assurance that your soul won't be demon chow when you die. This assumes a good or neutral person person.

[Lincoln Hills]

Yes: when you're trapped in a 30' pit and the black pudding is oozing into the hole after your, or you plummet off a cliff so high that the farmhouses below look like postage stamps, or you realize at the midnight meeting that you're the only member of the local Thieves' Guild that is not a vampire, you have somebody to blaspheme against just before you die.

More seriously - if your character doesn't have a religious background trait or a divine class that requires it, having a patron deity is simply a matter of flavor and choice. The exception are GMs that like to spring divine interference - sorry, I meant "intervention" on their players, but in that sort of campaign, being agnostic won't help you.

[MrSin]

You gain access to certain religion traits. Some of the religion traits happen to be more powerful than normal traits, in particular blade of mercy. Some divine related abilities affect people who follow the same religion, but I think that's mostly there to give a theme to encounters or parties.

Oh! And there isn't a chance Pharasma feeds you to Groetus when you die. If I remember right that's a thing.