The Y chromosome is so much shorter than the X because there are much fewer genes & much less genetic information stored in that chromosome. This is because the Y chromosome can’t have any absolutely essential genes, because roughly half the population doesn’t have a Y chromosome and still needs to fully function & survive. The Y chromosome mostly contains genes related to triggering male development, but the genes that actually control male development are on many different chromosomes (including the X).

Everyone has at least one X chromosome, and in fact the X chromosome does contain some essential genes, which also speaks to its length.