Can "Since" Ever Mean "Because"?
Dos and Don’ts are easy to teach, but they should be grounded in some reasoning. If they make no sense, we need to question them. The only reason we might not use since instead of because is that we fear sending our reader a short way down the conjunction path, when we want her on the temporal path; but even there, she will quickly adjust. (See Tip: “The Myth of However.”) So the only reason is not a good one.
Here are three writers I would trust before I continued to listen to the rants of Ms. Earleywine, still echoing in both ears
E.B. White in The Elements of Style (1955)
Since you are out of sympathy for cats, you may quite properly give this as a reason for not appearing at the dedicatory ceremonies of a cat hospital.
Richard Henry Dana in Two Years before the Mast (1840)
We were now well to the westward of the Cape, and were changing our course to the northward as much as we dared, since the strong southwest winds, which prevailed then, carried us in towards Patagonia.
William Shakespeare in Romeo & Juliet (1595, give or take)
That thou her maid art far more fair than she:
Be not her maid, since she is envious;
Her vestal livery is but sick and green
And none but fools do wear it; cast it off.
And none but fools suffer usage “rules” blindly. If you can’t see the logic behind them, cast them off.