Unfortunately I can’t give you a one size fits all answer because different breeds generally have different coat types. Rest assure I can simplify this slightly. There are six basic coat types, Smooth coat, Wire Coat, Double Coat, Curly Coat, Long Coat and Hairless Coat. Each of these coat types needs a different level of care.
Firstly your smooth and Hairless coats will not need to be shaved in fact in cooler months breeds with these coats may even need jumpers to keep warm, Hairless dogs will also need sun protection to avoid burns. These dogs may not need to be brushed or shaved but they still need to be bathed.
Curly coated dogs like poodles are A-OK to shave but they still need to be brushed regularly to avoid knots and burs, shaving them does not mean you can stop brushing them they can get burs and knots even after a short shave.
Double coated like Huskys and Shetland sheep dogs dogs surprisingly should never be shaved the double coat acts as insulation and helps to keep them cool in hot weather and warm in cold weather. When this the coat shaved they are more likely to overheat. When a double coated dog is shaved it becomes at risk of sunburn as they have less protection, once a double coated dog is shaved the condition may be permanently ruined as the coat will not be able to grow back as it naturally developed through puppyhood (the result will be much like the dog pictured above.)
Dogs with Long and wire coats do not have an undercoat and will need regular grooming and trims but should not need to be shaved unless they are extremely matted, shaving them will offer little to no benefit remember to brush and bath these dogs frequently to avoid such problems.
The most important thing to remember is to keep your dogs coat bur and knot free through brushing and if you use a groomer be very specific with your instructions there are far too many horror stories about double coated dogs being clean shaven after asking for a ‘tidy up’
(Pictured above Shetland Sheepdog Aggie who was shaved by mistake when asked for a ‘tidy up’)