Some people might shy away from clipart because they don't think of it, or they think it's too much work. If you find the clipart in a clipart book that will be too much work and it won't look good because you'll have to use a photocopier to resize it and then the quality degrades.
Often, photographs and pictures will be animated, making them perfect for different occasions like weddings, birthdays and holidays.
Yes, many think that branding is only important in fast food and retail operations, but it's extremely important to colleges that have to compete for student tuitions; and it's even gaining importance among high schools, and their surrounding communities, that are vying for prestige to boost neighborhood reputations/value. More successful high schools are now recruiting star athletes and students with high academic achievements, and the school's reputation can either help or hurt those efforts.