Nobody signs up for vendor lock-in. It is not a line in the contract you missed; it accretes quietly, in the shape of how the software stores what you give it. Five years in, your catalogue, your customers, your stock history, your invoices and your passports all live inside one company's system — and the question of whether you could ever get them back out was never asked, because everything was working.
Then something changes. The vendor is acquired and the product is "sunset". The pricing triples. The roadmap veers somewhere you don't need to go. Suddenly the only thing that matters is the one thing you never checked: can you leave, and what comes with you when you do?
For most business software the honest answer is "not easily". Data sits in a shape only the vendor's app understands; export is a screenshot or a PDF; the real records, the structured machine-readable ones, never leave the building. That is lock-in. No malicious clause, just a door that only opens inward. The remedy is to ask, before you commit, the questions you'd otherwise only ask in a crisis.