Why shouldn't I declaw my cat?/How can I save the furniture?

Declawing for non-medical reasons is very much a North American thing. It caught on in the 1970s and quickly came to be seen as THE way to stop a cat from scratching the furniture. Few owners thought at all about what it entailed or what it meant for the cat.

That's been changing over time and now declawing is coming to be seen as something cruel and unnecessary. 

Colleges that regulate the profession of veterinary medicine have reclassified declawing and define it now as "Unnecessary Veterinary Surgery (Cosmetic Surgery.)" The Ontario College of Veterinary Medicine issued a guideline in 2012 explaining the implications.

Professional associations (provincial, state and national) have been, in recent years, issuing progressively more strongly worded cautions about it. In July 2014, the American Veterinary Medical Association (AVMA) amended its policy on the declawing of domestic cats to clarify that the procedure is major surgery involving amputation and states that "it's the obligation of the veterinarian to provide cat owners with a complete education with regard to the normal scratching behavior of cats, the procedure itself, as well as potential risks to the patient." 

Advocates of animal welfare have also been voicing concerns. The ASPCA's current position statement, like those of SPCAs and Humane Societies across the US and in Canada, expresses strong opposition to declawing cats simply for the convenience of their owners.

Local SPCAs, Humane Societies and Rescue Groups are actively discouraging declawing and educating about alternatives. Today, when people adopt they are being told about the effectiveness of scratching poles, nail clipping, 2-sides tape, etc. and often they're being asked to sign adoption agreements that include a "will not declaw" clause.

On June 28, 2015, The Cat Clinic here in Hamilton announced that they had decided to stop performing declawing (including laser declaws) on cats. Their decision was one the veterinarians and staff had been contemplating for quite some time. Their reasons included post-surgical complications, pain, and the risk of new problems like urinating outside the litter box. Their detailed explanation (provided here)  is something anyone considering declawing a cat should read.
 
There's a growing list of clinics in Canadian provinces and US states that are coming to the same conclusion and making similar announcements. And each clinic that stops offering the service is taking Canada and the US closer to making declawing "a thing of the past."

Most North Americans are surprised to hear that declawing is already illegal in at least 22 countries, including England, much of the EU, Australia, Japan and Israel. In 2015 New York may become the first US state to make declawing illegal.

To the question, "How can I save my furniture without resorting to declawing?" there are a variety of answers - all more humane than declawing. These links provide ideas to explore:

http://m.wikihow.com/Stop-a-Cat-from-Clawing-Furniture
http://www.catscratching.com
http://www.littlebigcat.com/important-information/declawing-alternatives/