I think BJT and FET are the most basic active elements to start with when teaching new professionals. The transistors are considered an important building block in the industry today, so it's important to start with it when dealing with active elements.
The tubes have been replaced by the transistors, because transistors consume less space and are more efficient and the industry today is looking for the minimum space to achieve the highest performance. In my opinion, teaching tubes is essential to understand how we reached the technology we have today but at the same time, the focus should be more on transistors as they are the most commonly used today.