The concept of antiques as investments took off in the 1980’s. The number of people that saw opportunity in buying and selling English furniture permanently altered the market and propelled prices skyward. A sleepy, often genteel trade became a market.
There is a flaw in selling decorative arts, particularly furniture, as investments. The flaw is that not all people see things in the same way. Put aside the charlatans whose intent was to defraud and you still had people looking at furniture from different points of view. Any ten dealers will disagree on what constitutes good color, proportion, quality, timber choice and, of course the style that is their favorite.
Everything has a value of course. Antique dealers see value and try to maximize it in their trading. That is not investment, it is a business. For buyers, antiques should be a stylistic preference. Personally, I like good design of any era and any country and I will buy it if the intrinsic nature of the item truly appeals to me. I am on a budget but most people are. For me, that is all the investment I need.