“Insurance is sold, not bought” is a popular axiom of the insurance business (especially for life insurance), cited in print since at least 1916. Insurance can be complicated and, unless purchase is required by law, it’s often put off by a potential purchaser. A professional and knowledgeable insurance salesperson can sell insurance—a field where potential customers usually don’t walk in the door prepared to buy the product.
 
The “sold, not bought” expression has been used in other fields besides insurance, with a popular variant being “Local advertising is sold, not bought.”
       
   
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13 May 1916, The Weekly Underwriter, “Business Builder” section, pg. 1 (after pg. 562), col. 2: 
Because our particular commodity — insurance — is sold — not bought — we have to solicit (and solicit hard) our business.
 
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March 1917, Annals of the American Academy of Political and Social Science, “Modern Insurance Problems,” Vol. 70, ‘The Disability Insurance Policy” by A. P. Woodward, pg. 236:
Disability insurance is sold—not bought, and its sale requires the entire time of a large body of highly trained and efficient salesmen.
 
10 March 1918, New York (NY) Times, pg. X8:
SOLDIERS’ INSURANCE ABOVE $10,000,000,000; Ninety Per Cent. of Men Service Protected, Including Sailors—In Some Units Every Man Has Full $10,000 Policy.
By LAWRENCE PRIDDY, President of the National Association of Life Underwriters
(...)
At the time of the passage of this act those representatives of the government who were particularly instrumental in the passage of the measure believed that with the passage of the bill there would be a tremendous demand for this insurance but it was early discovered by them that the demand had to be created, that “life insurance is sold and not bought,” and this notwithstanding the fact that the guarantee back of the contract is the United States Government itself, and that it is offered at a cost to the insured of about one-tenth of what it will cost to provide the insurance.
     
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24 April 1918, The Insurance Press, pg. 9, cols. 1-2:
Realizing that Insurance Is sold — not bought: that the superior service so valued by the assured is due in large measure to the knowledge and hard work of agents and brokers, it believes both are essential to the business, and that to eliminate either would be detrimental to the best interests of the general public.

30 September 1930, Aberdeen (SD) Evening News, “U.S. Insurance of War Vets Is Over 3 Billion,” pg. 5, col. 1:
Unfortunately nothing is truer than the aphorism that life insurance is sold, not bought.
 
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Personal Finance
Third Edition
By Lawrence J. Gitman
Chicago, IL: Dryden Press
1984
Pg. 310:
“Life insurance is sold — not bought” is an axiom in the life insurance business. As a rule people seldom get a strong urge to buy life insurance as they might a house, car, or a new television set.
   
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The Individual Investor’sGguide to Low-Load Insurance Products
By Glenn S. Daily
Chicago, IL: International Pub. Corp.
1990
Pg. XI:
“Life insurance is sold, not bought” is one of the insurance industry’s favorite sayings. Why do we need agents? Because life insurance is sold, not bought.
   
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Health Financing for Poor People:
Resource mobilization and risk sharing
By Alexander S. Preker and Guy Carrin
Washington, DC: World Bank; Geneva: Worlh Health Organization: International Labour Office
2004
Pg. 153:
Insurance literature has long documented that most people lack the appreciation for the benefit of insurance, a fact that led to a common saying: “Insurance is sold not bought.”
     
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Private Wealth:
Wealth Management in Practice
By Stephen M. Horan
Hoboken, NJ: Wiley
2009
Pg. 21:
Never forget the old saw, “Insurance is sold, not bought.” The same goes for stocks, bonds, and lottery coupons.