Because you don't have to worry about plumbing, roofing, or ac/heating. Condos are good starter homes. Very little responsibility. All you have to do is pay an HOA fee of like $150 a month which includes housing insurance. Most big condos have pools, gyms, libraries, etc. Plus...electric bills are cheaper to warm and cool your house.
The only disadvantages to a condo I could think of is no backyard (I don't want a backyard), and the fact that people are on either side of you and above/below you. Nice condos have thick walls between units so you really don't hear your neighbors unless they are just drymounting crazy.