perhaps its not applicable to those who didnt qualify the criteria due to whatever reason..
example people in ISS (international space station).
funny POINT to ponder, its really impossible to do SEX in space station due to gravity lmao.... 
and if you go for fasting from FOOD & DRINK then its only like one hour fast and more than 15 fasts in a day.
people in polar regions where they can have (long nights/permanent dark) lasting for months. so they are chilling there..
these type of situations i guess thats why author of QURAN say whoever witness the shahr-e-ramadhan.
شَهْرُ رَمَضَانَ ٱلَّذِىٓ أُنزِلَ فِيهِ ٱلْقُرْءَانُ
The month of Ramadan is the month during which the Qur?ān was compositely sent (to the chosen sincere allegiant Muhammad on appointing-assigning him the responsibility of the final Universal Messenger-Spokesperson) ?
هُدٙى لِّلنَّاسِ
It (Qur?ān) serves as guidance for the Mankind ?
وَبَيِّنَٟتٛ مِّنَ ٱلْـهُـدَىٰ وَٱلْفُرْقَانِۚ
And distinctly self explanatory verbal passages were gradually communicated from the miscellany of Al-Huda'a: the Guide (Qur?ān) and Al-Furqau'n: the Criterion; the Separator of right from wrong, fact from falsity-conjecture.
فَمَن شَهِدَ مِنكُـمُ ٱلشَّهْرَ فَلْيَصُـمْهُۖ
Therefore,
if he who reaching adulthood among you was present at home in this month, thereat, he should observe it by fasting.وَمَن كَانَ مَرِيضٙا أَوْ عَلَـىٰ سَفَرٛ
And if anyone has been suffering from sickness, or was embarking on a journey ?
فَعِدَّةٚ مِّنْ أَيَّامٛ أُخَرَۗ
Thereby (he may adjourn fasting) the count be accomplished during the days of another-later month.
يُرِيدُ ٱللَّهُ بِكُـمُ ٱلْيُسْـرَ
Allah the Exalted intends easiness for you people ?
وَلَا يُرِيدُ بِكُـمُ ٱلْعُسْـرَ
And He the Exalted never intends difficulty-awkwardness for you ?
وَلِتُكْمِلُوا۟ ٱلْعِدَّةَ
And its purpose is that you might complete the count of fasting ?
وَلِتُكَـبِّـرُوا۟ ٱللَّهَ عَلَـىٰ مَا هَدَىٰكُـمْ
And that you might proclaim and praise the Sublime grandeur of Allah the Mightiest upon your getting aright guided (by adhering to Qur?ān) ?
وَلَعَلَّـكُـمْ تَشْكُرُونَ .2:185١٨٥
And so that you people might keep expressing gratitude. [2:185]
Both the sentences are conditional --- the opposite of a person on journey is the person who is at home.
Interestingly the basic perception of Root: ص و م
bn Faris [died 1005] stated:
(مقاييس اللغة)
الصاد والواو والميم أصلٌ يدلُّ على إِمساكٍ وركودٍ في مكان. من ذلك صَوم الصَّائم
That it leads to the perception of abstinence, and stasis - stagnancy at home.(لسان العرب)
الصَّوْمُ: تَرْكُ الطعامِ والشَّرابِ والنِّكاحِ والكلامِ
Fasting is the act and state of abstinence of activity relating to food intake and genitalia and speech.
