Pedantry: they aren't the same horses, though: in 1915 they were mostly draft horses, with a few sport/pleasure; in 2023 they're mostly sport/pleasure, with a few draft.

Porsche engines are clearly sport/pleasure engines, not draft engines.

True; looks like their last tractor was over 50 years ago.

Other marques are still extant:

https://www.ferraritractor.com

https://www.lamborghini-tractors.com/en-eu/

In the meantime the human population quadrupled, so the actual demand for horses is not half, but closer to 1/8 of what it was.

They'll go the way of horses in the sense that you'll be hardly seeing any in cities.

You seem to be using “actual” in a way that suggests proportion to population is a key part of the definition. But although a company that served a market for 20 million might well have failed as the market shrank, it also had the opportunity to survive and continue serving an actual market with an actual demand for 7 million actual horses.

Hermès' original market for tack (harnesses and bridles for driving) shrank considerably, but they've found new markets since.

Lagniappe: https://www.youtube.com/watch?v=qs-IKeRyRAg

Something that surprised me: the German army in WW2 was mainly horse drawn.

According to the below link, 80% of its transport was via horse.

https://www.zdnet.com/article/the-wwii-german-army-was-80-ho...

I believe this has a lot to do with the failure of the Maginot line: it had been constructed to slow down an army with horse-drawn logistics (after all, germany had no oil) but the germans did their end run with mechanised units (having researched synfuels in the meantime).

From 1940 to 1943, one can readily explain Axis strategy as an insatiable quest for more oil: no barrels, no Blitz.

EDIT: Lagniappe: https://en.wikipedia.org/wiki/Joe_Medicine_Crow#World_War_II

Reflecting the interwar German society more broadly; agricultural mechanization was decades behind the US and UK.

The industrial and economic "miracle" of the pre war Nazi regime wasn't spent on tractors either, but on weapons.

Were horses ever actively restricted by governments around the world or did we move away from them because better solutions were available?

They were causing environmental problems, cities were clogged up with horse shit. I don't know whether that influenced the transition though.

The question was only if there was ever regulatory action taken to limit the use of horses the way we are seeing in relation to internal combustion engines.