The PIE homeland (i.e., the area that is generally considered to be the PIE homeland, the Pontic-Caspian steppe) is salt-rich. Salt is available from many salty low-lying areas in the steppe, and also readily available from the seas in the area (the Black Sea, Caspian Sea, Aral Sea). Perhaps most spectacularly, the salt-lake Lake Baskunchak, sometimes called the "Second Dead Sea", lies in this area. Salt deposits are readily found on the lake shores:
and have been exploited commercially since the 8th century AD if not earlier, the salt moving along the trade routes that cross the area (i.e., the Silk Roads). Today, the lake supplies about 80% of Russia's salt, with well over 1 million tons of salt mined per year on average. The salt was carried by camels into the 20th century, when a railway was built for the salt trade.
Lake Baskunchak is only one of many salt lakes in the area; others include Lake Mazna-Khag, Lake Manych-Gudilo, Lake Elton, Lake Khanskoye, Koyashskoye Salt Lake, and many smaller lakes.
Today, salt is the universal flavouring used in the area, and is the most important "spice" in traditional Kazakh cuisine. Traditionally, salt was important for preserving food. For PIE pastoralists (who would probably get all of the salt they needed in their diet from the dairy and meat in their diet, without needing to add any), the only essential use for salt would have been for dried meat (and it's not strictly necessary even for that, but is certainly useful for it). Dairy products can be preserved by fermentation, but salt is used in the making of some preserved dairy products. PIE farmers, with a more plant-based diet, would have had more need for salt, but as noted, they lived in a very salt-rich environment, and could easily have obtained salt either locally or by trade.
