Adding to what everyone has said, I think another significant factor is the lack of a dedicated UX team in many B2B companies. While B2C companies often have robust UX departments, B2B firms might not invest as heavily in UX resources. This means that UX considerations can take a backseat to development speed and feature delivery.
Furthermore, B2B products are sometimes seen as utilitarian tools rather than experiences that should delight users. There's a misconception that because the software is for professional use, it doesn't need to be enjoyable to use. This mindset overlooks the fact that good UX can lead to greater efficiency and job satisfaction, which ultimately benefits the company.