Read the following text to answer the question bellow:

According to Dudley-Evans and St John (1998,10-11), there are several widely-believed essential advantages of ESP courses: they are more motivating than EGP courses as they focus on the learner’s needs, more cost-effective, and the aims are widely accepted by learners. However, the level of motivation depends on the individual learner especially in ESP as learners seek variety from the commonly addressed topics. The problem here is that it is, naturally, easier to do specific work with highly motivated students whereas with less motivated students teachers tend to stick with more general work and topics. In ESP, it is crucial to present any teaching activity in a context regardless of the aim. Dudley-Evans and St John distinguish in this respect “carrier content” and “real content” (1998, 11): carrier content describes an authentic topic to teach the real content which is the language of process.
KOPPITSCH, Gerlinde. Teaching English for Specific Purposes. An action research project. Master Thesis. Alpen-Adria-Universität Klagenfurt, Klagenfurt,2019.

According to the text, what is a crucial aspect of teaching English for Specific Purposes (ESP) courses?