Depends on the size of the company. Perhaps you're simply not the target customer for that company, you self-select out of their customer pipeline which makes it easier for them to handle costs, as it is more expensive to maintain separate SaaS and one-time versions (essentially on-premise, which is often much more expensive and for enterprises who can afford them due to said hassle). However, some solo devs and smaller companies do exist that make only one-time purchase products, because they don't have much overhead.