It's the name. "Picasso" sounds similar to names like "Michelangelo", "Leonardo (da vinci)", and "Raphael" (short but not too much, easy to remember, and pleasant to the eye/ear). It's also a very uncommon name. Hence why we are tempted to associate a famous painter named "Picasso" with the distant past. Like we would associate a painter named "Jennifer" or "Peter" with more modern times.