It has a big effect on auto sales and clothing sales. It's the first weekend some people can come out of their homes and see the back yard. It also gives companies an extra day to plan an prepare during a weekend when there aren't any religous activities or family activities to interfere. It should be called CEO's day, not just Presidents Day. So in essence, yes, Presidents day is a three day business oriented weekend holiday with no real family or religous activities to clog up the 36 hours of business "up-time" with "market-down-time".
It's a great time for a lot of businesses to get their employee's taxes done on Saturday, a lot of companies to do a mini-stand-down and spring cleaning also.