Present Simple or Present Continuous with "these days"

"These days" express the period around now. Then, I wonder, why is used the Present Simple in the following sentence?:

• These days I travel a lot. I’m spending more and more time away from home. (Considering the rule given above, I would say: These days I am travelling a lot.)

I've also come across the sentence where both tenses are considered correct:

• These days, more and more people prefer / are preferring to retire early.

So, is it optional whether we use present simple or continuous with "these days"?

Answer

The present simple can also refer to things in the period around 'now'.

It can be used for statements of general truth ("the sky is blue") or for conditions that pertain ("I know how to change a lightbulb"). When used with an adverbial of time, they might also be used for statements of general truth ("in the morning, I prefer not to speak to people") and provide for a condition as part of that statement. However, an adverbial of time can also accompany a statement of current conditions ("right now, I am hungry"), provided that the adverbial of time involved includes 'now'.

The progressive aspect refers to ongoing or recurring actions, and so can also be used for things that are located in time around now. "I am travelling a lot these days" is essentially equivalent to "I travel a lot these days". A key point that must be understood about English is that there is not always only one verb form/tense/mood/aspect that is correct.

Preferring is a somewhat special case, though. It is rarely used in the progressive aspect. Indeed, I'm racking my brain for cases of use of the -ing form at all, and mostly it's used in various adverbials.

"They were offered the choice of pinot noir or pinot grigio. Preferring red wine, Susan chose the pinot noir."

(I'm not actually sure if it's being a gerund or a participle in that case)