Is there any historical reason why the hot water is usually on the left of the sink?

First, it is indeed a standard; The Uniform Plumbing Code (by the International Association of Plumbing and Mechanical Officials) specifies that

[Faucets] shall be connected to the water distribution system so that hot water corresponds to the left side of the fittings ... to assist the elderly and disabled (especially the blind) in identifying which tap is the correct one to use.

That's form the newer edition. I can only find the 2009 copy online for free, which has slightly different wording (see sec 601.3).

Secondly, I've never seen a reliable history on why they chose this to be the standard. There are lots of details and further sources in Inside the Victorian Home: A Portrait of Domestic Life in Victorian England by Judith Flander that shows how the bathroom sink evolved from cold-only hand pumps before 1860 to hot water being available from a distant location and finally, starting in the 1880s, to a combined hot and cold faucet we see today.

She doesn't address the handedness but in all of the illustrations and artifacts we can still examine, the pumps were almost universally installed to be used by the right hand and, once hot plumbing was available, landlords would just put it on the left. Again, this may or may not have anything to do with why the UPC set that standard or why it became the more common practice.