Generally speaking, this is true. The typical Spanish student sees an English class as a way to relax. A break from the stress of everyday life. Chill out, speak some English and have fun.

 In some northern European cultures, the opposite is true. students insist on learning grammar for most of the class. Not so in Spain!

Sometimes a teacher tells me that their class is going fantastically well- "We spend the whole class chatting". On hearing this, I try to talk the teacher into changing their method. Sometimes they don't and invariably the complaint from the client comes through.

Any native speaker can have a "chat" with an English language learner. But a qualified, experienced English teacher understands the need to use appropriate techniques so students improve.

What's the problem with speaking for all the class?

Firstly, even if it's a conversation class, a teacher must correct mistakes. This involves telling the student what mistake they have made, explaining the correct way to say it, and if necessary explain the grammar points involved. If a student is not corrected, then while their fluency will improve, their use of structure will not, and in fact the mistakes will be reinforced by repetition.

Secondly, speaking is only one part of language learning. What about listening, reading, writing and grammar? Whether you like it or not, grammar and structure underpin language. A student who constantly speaks without understanding the structure of the language will never improve. Even if its for only 10 or 15 minutes, every class should include some grammar. This doesn't necessarily mean formal exercises, but can often be off-the-cuff grammar points explained and practiced in response to a student error.

Finally, in my experience, after 2 or 3 months of "chatting" in class, students realise they are not improving.  As an English teacher, can you really hold a conversation for 2 or 3 hours a week for month after month without repeating yourself? How many times can you speak about the weekend or football results without becoming boring? After a few months of this type of class, either the student complains or just stops coming to class.

Remember, you are a professional teacher. Use your training and experience to improve your students' level of English.