Turtles have been popular for a long time. Baby red eared sliders were readily available and inexpensive many years ago, which unfortunately resulted in a lot of neglected turtles. They were often sent home with tiny plastic bowls with a little plastic tree (unfortunately these are still sold with turtles in some places). With no filtration system and no room to grow, these little babies didn't have much chance. In the 1970s, the US government banned the sale of turtles less than 4 inches long, once the connection was made between turtles and Salmonella infections, especially in children. It is not that baby turtles carry more Salmonella than larger ones; it is more of a case of children being more likely to handle the smaller turtles (and/or put them in their mouths!).
Sadly, many turtles are still sold to people who have little idea how much care turtles require, including large tanks, special lighting, good filtration and lots of cleaning. Even worse, they are sometimes given out as prizes at fairs and at other events. All too often aquatic turtles die due to stress and neglect - and sometimes they suffer so much stress, overcrowding and neglect during transport and in shops (and fairs) that even if a new owner provides ideal care the turtles may be so ill they die anyway.
Turtles and Children
Turtles are not ideal pets for children. They are not easy to care for, not great for handling, and in addition they often do harbor Salmonella bacteria which can be passed to the children who don't understand the need for careful hygiene. Many children do not have the interest or ability to provide the amount of care and cleaning that a turtle rightfully requires, so parents must realize the responsibility for care ultimately falls to them if the kids lose interest.
Size and Life Span
Many people also do not realize how big aquatic turtles can get. Red eared sliders and a couple of the other commonly available pet species will grow to at least 10-12 inches long and thus will require correspondingly large enclosures. All turtles have the potential to enjoy a very long life span (i.e. several decades!) if cared for properly.
Aquatic turtles require fairly elaborate housing. They need regular exposure to ultraviolet (UV) light, so pricey bulbs designed for reptiles that produce UVA and UVB light are needed for turtle tanks. Without this light, metabolic bone disease (soft shell syndrome) can result. Turtles are messy, and a good filtration unit will be necessary to help maintain water quality, as will regular cleaning. They should have deep enough water to allow swimming, along with a place to get out of the water to bask (heated from above with a basking light.) In addition, appropriate water and ambient temperatures should be maintained.
Although turtle foods have come a long way they are not recommended as a sole source of food for aquatic turtles. Most are omnivores (and preferences for different foods might change at different points in the life cycle), and offering a good variety of foods is the best way to feed most turtles. As a rule, feeding turtles in a separate plastic tub will allow the mess associated with feeding to be contained (turtles are messy eaters, and this will reduce the need for tank cleaning a bit) and allow monitoring of food intake of each turtle if multiple turtles are kept.
But for the Right Owner...
Having said all that, given the right person and the right commitment turtles make beautiful, fascinating, and enjoyable pets. The first step is to research the species available and the care required by each. While the basics of aquatic turtle care are similar for all species, potential owners need to consult specific care sheets for details on housing, environment and feeding for the species in which they are interested.
For beginners, the hardier turtles are recommended, such as red eared sliders, cooters, and mud and musk turtles, keeping in mind that sliders and cooters will reach a mature length of greater than 12 inches, while mud and musk turtles are about half that size. Map and painted turtles, as well as some of the less common species are a bit less hardy. Softshell and snapping turtles have a reputation for being large, aggressive, and generally more difficult to care for so are not good for beginners.
Beyond providing a proper environment and diet for aquatic turtles, they do not need a lot of attention, although regular interaction may result in a tame and sociable turtle. In any case, they are lovely and if properly cared for should provide years of enjoyment.
For further information on specific care of aquatic turtles, see the Aquatic Turtle Links.