Aliyah l'regel, literally ascent on foot, was a central practice of Judaism almost from its origins. The Bible declares, "Three times a year shall all of your males appear before the Lord your God". On Pesach, Shavuot and Succot, many thousands of familes (and not just males) would go up to celebrate the holidays in Jerusalem. Arguably, aliyah l'regel was the original, prototypical pilgrimage experience.
After the destruction of the Second Temple, Jews continued to make pilgrimages, now tinged with sadness to Jerusalem. Today, with no Temple, there is no commandment to do aliyah l'regel , but the impulse is still there, as myriads throng to Jerusalem during the holidays and it was almost impossible during Succot to find a free taxi, restaurant table or seat at the Kotel.
You might think that it was called aliyah l'regel , ascent on foot, because there were no cars or planes in biblical times. But we see from the sources that there is an important element of humility involved in going by foot. The Mishnah teaches that even a king would dismount when he reached the temple gates and carry his own basket of first fruits on his shoulder (Bikkurim, 3:4).