A puppy is not a toy
A puppy is a living being who has a need for love and proper care for the rest of his life. A puppy is especially vulnerable to broken bones and other injuries from careless treatment.
A puppy is not a teaching aid
A puppy should not be obtained to instill a sense of responsibility in children. It is unfair to place an animal's entire well being in the hands of children. Feeding, grooming, housebreaking, and discipline training of an animal should be the principal responsibilities of adults. Responsibility training of children is better left for household tasks, where a helpless animal's needs are not at stake.
A puppy is not cheap
The adoption fee for a pet is a mere pittance compared to the cost of veterinary care for routine and emergency treatment over a dog's life, as well as licensing fees and damages to personal property which are bound to occur.
A puppy is not a gift or a spur-of-the-moment commitment
Animal shelters are overrun with dogs who were acquired for the wrong reasons or without sufficient investigation and personal commitment.
A puppy is not self cleaning
Dogs can neither groom themselves, nor clean up after themselves (accidents, shedding) and impose additional workload in a household.
A puppy is not an adult dog
Having neither the physical nor the mental abilities of an adult dog, a puppy cannot wait long periods of time before relieving himself, nor differentiate between what is a toy, and what isn't, nor distinguish between digestible and dangerous objects. They require patience, understanding, and supervision just as with human infants and young children. A puppy doesn't mature into an adult dog for at least two years. If you work and don't have time for training and play, get an older dog.
A puppy is not a puppy forever
But they need your love and care forever. Be sure that you understand the near-term and lifelong commitment involved, before succumbing to the charms of a cute little puppy.