It has become a common habit among Muslims, to say wallahi at least once in every sentence they utter. Through experience I know it's more rife among some nationalities/communities than others.
Swearing by Allah is a very serious matter. Doing over little thing show, how much you think of your Lord Most High.
"The best of people are those of my generation, then those who follow them, then those who follow them, after which there will come a people whose testimonies will precede their oaths and whose oaths will precede their testimonies."
(Narrated by Bukhari and Muslim)
This Hadith discourages frequent swearing. People rush hastily into swearing oaths and bearing witness before they are requested to do so, as if these matters are of little moment. This reduces respect for the name of Allah
And do not obey every worthless habitual swearer
[Al Qalam, ch 68:10]
And do not obey every Hallaf (one who swears much) Mahin (liar or worthless person).) This is because the liar, due to his weakness and his disgracefulness, only seeks protection in his false oaths which he boldly swears to while using Allah's Names, and he uses them (false oaths) all the time and out of place (i.e., unnecessarily). Ibn `Abbas said, "Al-Mahin means the liar.''
Tafsir Ibn Kathir
The Messenger said:
'Three people Allah will not talk to them, nor will He purify them, and they shall receive a painful torment.'
In this Hadith the Prophet, enumerated among those three people.
A man who made Allah as his commodity. That is, buying nothing except by swearing by Allah, and selling nothing but by swearing by Allah. [At Tabarani]
So if we can't swear by Allah when doing trade, what makes us think we can do it for small things, like say "wallahi I drank coffee today", "wallahi my phone doesn't work" and all other nonsensical oaths.
So let's stop this foolishness, and stop belittling the worth of our Creator ,Allah , lest we be called to account for it on the Day of Judgement