Some years ago (even when I started my career as a designer), protecting your intellectual image property was much more important that it seems to be today - others sharing your work online might have been regarded as image theft, as if sharing and image for free would somehow devalue it.
To see your work, customers would have to stumble upon your website, or see a magazine feature or advertisement in a magazine. Smaller businesses who didn't have the capital to invest in expensive advertisements or pay and SEO optimiser to make sure their website came up on the first page of a google search might have struggled to be discovered in an oversaturated market.
Aside from word-of-mouth recommendations, accreditations and affiliations (BIID, SBID, ICD, The List House and Garden, HOUZZ), which are the traditional ways that a client might find an interior designer, social media in particular has changed the way people and businesses connect with each other - the great thing about this is that small businesses now have a platform to reach out to and interact with potential clients directly and for free.
Instagram has changed the way we reach out to our network of suppliers and clients - it has contributed to making the industry more open and protectionism and competitiveness is being replaced by a culture of sharing and support others in our network. Sharing really is caring. :)