"He always waits for me" is stating an action which is always true but is dependent on another clause.
"he always waits for me ...When I finish school"
He always waits for me when I finish work.
This means that the sentence is usually part of "the conditionals". This particular example is known in English grammar as the zero conditional and is formed with the present tense and present tense.
"We are always waiting for you" is not a depending on another clause, its simply a statement of fact at any time, the people are waiting for another person to contact them. Another way of saying "you are welcome anytime"
"Ice melts when I heat it"
"Ice always melts"
its the same thing