Why are lysosomes called a suicidal bag?

Lysosomes are organelles that were initially thought to serve the function of dissolving cells when those cells were about to die. The enzymes within lysosomes would burst out of it, dissolving cells from within. The term was invented decades ago, prior to the discovery of their other cellular-sustaining properties.
Lysosomes get their name from the word "lysis" which refers to the decomposition of cells. Lysosomes are responsible for digesting foreign particles that enter the cell through a process known as autolysis, which is divided into heterophagy and autophagy. Heterophagy is when lysosomes digest foreign particles; autophagy is when lysosomes release digestive enzymes to dissolve the cell itself. This is done when a cell is damaged or parts of the cell no longer function.
So, yes, lysosomes do bring about the end of a cell, but only when a cell can no longer function or is damaged. The term "suicide bag" sticks probably because it is hard to forget.