-ています / present continuous form not used in habitual action

Question

I have read this sentence in my book :

山田{やまだ}さんは毎朝{まいあさ}６時{じ}に起きます{おきます}。

• Why isn't the present continuous used (起きています) since it is obviously a habit for Yamada-san to wake up at 6 every morning?

• Is it because we already have 毎朝 in the sentence? But then, would it mean that the -ます form is prefered over the -ています form if the meaning of a sentence is clear enough?

• Then, does it sound weird to use the present continuous in that kind of sentences?

• If my assumption is wrong, what is the difference between this sentence and the same one with -ています form?

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To go further…

Could this sentence be translated to future as:

Mr Yamada will get up at 6 every morning.

Does it depend only on context or would we need to add some words to make sure we understand it as future tense?

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Ressources

• Wasabi-jpn.com "Customary Actions: the Plain Form VS. the Te-form + いる"

• From another book:

The -ています form can also be used to express a customary and repeated action that takes place through a certain period of time.

Examples:

ぎんこうにつとめています。 I work in a bank.

あねは英語{えいご}の先生{せんせい}をしています。 My sister is an English teacher.

Answer 1

Using ている form for habitual actions, compared with the one without it, implies that the speaker is to some extent conscious of period that the habitual action continues for.

In other words, 山田さんは毎朝６時に起きている implies that the speaker is conscious that Yamada wouldn't necessarily get up at 6 in past, and won't necessarily keep his habit forever.

So, the reason why it doesn't use ている form is that the speaker is not particularly conscious of sense of period as mentioned above.

In this regard, it sounds too fatal to apply permanent action, namely, habitual one without ている to what's generally introduced as examples of habitual actions in textbooks e.g. 学校へ通っている or 店で働いている.

When you consider an example like 人は空気を吸う, you won't really wonder why it's not ている, will you? 毎朝起きる is kinda in-between, but at least, it's not unnatural to use permanent action.

Answer 2

I wanted to edit user4092's answer, but it was too drastic. I've been advised by a moderator to make it a separate answer as it introduces new terminology.

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ている form - Temporary custom

Using ている form for customary actions, compared with just the plain form, implies that the speaker is, to some extent, conscious of a period of time that the customary action continues for.

山田さんは毎朝６時に起きている。

In other words, the above sentence implies that the speaker is conscious that Yamada wouldn't necessarily get up at 6 in past, and won't necessarily keep his habit forever. He wakes up at 6 "these days", it is a temporary custom.

So, the reason why it doesn't use ている form is that the speaker is not particularly conscious of a sense of time as mentioned above, or doesn't want to imply one.

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Plain form - "Permanent" custom

In this regard, it sounds too fatal to apply the plain form (without ている) as in a permanent action to common examples of habitual actions in textbooks such as:

学校{がっこう}へ[通]{かよ}っている。 I go to school.

店{みせ}で[働]{はたら}いている。 I work in a shop.

Consider an example like this one:

人{ひと}は空気{くうき}を[吸]{す}う。 Humans breathe air.

You don't wonder why ている form is not used, do you? Because it's not a temporary custom, but a permanent one.

毎朝起きる is kinda in-between. It's not unnatural to use permanent action but both forms are fine.

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Source: Wasabi-jpn.com on "Customary Actions"

Answer 3

According to "A Dictionary of Basic Japanese Grammar", page 155:

いる: Someone or something is doing something he or it started some time ago, or is in a state created by an action he or it took some time ago.

Examples paraphrased from the book:

彼{かれ}は酒{さけ}を飲{の}んでいる。
He is drinking sake.

彼{かれ}は話{はな}している。
He is talking.

彼{かれ}は食{た}べている。
He is eating.

If Verb-て is a verb indicating a momentary action which cannot be repeated, Verb-て expresses the idea that something happened to X and X maintains the state which was created by that event.

Examples:

山田{やまだ}さんは起{お}きている。
Mr. Yamada is awake. (Mr. Yamada woke up some time ago and still awake now)

リンゴは腐{くさ}っている。 (Example paraphrased from the book)
The apple is rotten. (the apple rotted some time ago, and is still rotten now)

Verb-ている also expresses a habitual action (...) Example:

山田{やまだ}さんは毎日{まいにち}４キロ走{はし}っている。
Mr. Yamada runs 4 km every day.

But in the case of punctual verbs, I believe the meaning above takes precedence.