Preposition with verb "provide"

Solution 1:

If you provide for [someone/something in need] without specifying exactly what, it means you make available to them whatever they need - often food (provisions/provender). You can also provide for [some eventuality] without specifying what, meaning you have plans/resources to deal with that eventuality should it come to pass. Both these usages have been around a long time, and always involve for, not to.

To provide [something] to [someone] is a far more recent usage...

Per @JeffSahol's answer, provide X to Y often implies that Y did actually receive X, whereas provide X for Y can be used even if Y doesn't avail himself of the X which is on offer. But often it's an idiomatic choice where people repeat the version they hear most. Other than that, the modern trend towards to clearly disambiguates from the first two usages given above.

Solution 2:

One shade of difference is the assumption that someone providing x to has actually delivered x to the person, not merely made sure that it was made available:

• If you provided umbrellas for your guests, that means that there is a supply of umbrellas available for their use.

• If you provided umbrellas to your guests, I would be more likely to assume they each have an umbrella in their hand.