The space between lines in a paragraph is called Leading, a term harkening back to the days of metal type. How much or how little leading to use depends on several factors including the font, font size, and the line length or column width. Since the viewer is concentrating on content, the goal is to make the reading as distraction-free as possible.
Lines that have too little space between them after considering all of the above factors feel cramped and uncomfortable to read, perhaps even causing the reader to jump ahead a line. Lines that are spaced too far apart feel disconnected with the jump to the next line being too great, causing a break in the reading flow. Lines that are well spaced given the specific circumstances feel comfortable to read.