If we say:
I always do
It shows that some time ago I started doing it, then continued, continued and then it became "now" and I can say '"always" because my action has some statistics, some experience.
But this is the exact case of using Present Perfect Continuous
I have always been doing.
I see no difference between them. Both started in the past and happen now
According to [ESL/base.com][1],
"Some verbs are not usually used with present perfect continuous because they are not action verbs, for example: believe, belong, depend, hate, know, like, love, mean, need, prefer, realise, suppose, want, understand." An example they give is:
"I‘ve known him for ten years." – correct
"I‘ve been knowing him for ten years." – incorrect
I do have doubts about whether some of the verbs in their list belong there. For example, "He had been needing reliable transportation ever since he got that job." sounds fine to me. And "It's obvious I have been understanding that parable all wrong." is equally idiomatic. But it is clear that there are some cases where we would use the present tense, and the present perfect continuous would just be inappropriate.
For example:
"Freesia flowers always smell divine."
NOT "Freesia flowers have always been smelling divine."
And
"Carbon always forms covalent bonds"
NOT "Carbon has always been forming covalent bonds."
However in situations where it is idiomatic to use that present perfect continuous tense at all, you are right that with "always", you could substitute the present tense with no substantial change in meaning.
I always peel the carrots before cooking them.
vs.
I have always been peeling the carrots before cooking them.
or
He always uses the back door.
vs.
He has always been using the back door.
Both pairs of sentences state the same basic facts. As you say, "both started in the past and happen now". And when you say "always", it describes a situation that has never been any different up to now.
Neither verb tense addresses what might happen in the future though. Either one allows the possibility that the action that "always happens" or "has always been happening" might change starting now.
In my opinion, there is a subtle suggestion of temporary-ness with the second options (... have always been ...-ing), a slight implication that things might be about to change.
Of course it depends on the context, but if you say, "We always park here," it sounds like a simple fact: that's where we park. But "We have always been parking here," seems to be a little more complicated, maybe because we need to imagine an explanation for the extra words in that verb tense. To my ear at least, the second options carry an unspoken follow-up idea of, "..., but now ..."
But the difference between your two verb tenses, if any, is only one of nuance, not substance.
