If you're outside of Europe, it really depends on the country. Some countries it might be Telegram, Whatsapp, Line, WeChat, etc. There's no real universal standard.
SMS is still more reliable because it doesn't rely on cellular data service. In emergency situations when cellular networks are overloaded or with a weak connection it's more likely to get through.
Don't forget - SMS was a hack in the system messages:
> The key idea for SMS was to use this telephone-optimized system, and to transport messages on the signalling paths needed to control the telephone traffic during periods when no signalling traffic existed.
In the absence of internet connection yea SMS is still useful but it has nowhere near the quality of UX and features of mobile messaging apps. It is just communication protocol after all.
Plus SMS uses phone signalling, like 2G does, and 3G data a bit. It needs a lot of signalling bandwidth where data and voice, ironically, do not need as much. SMS will fail long before data or voice on cellular networks fails. It has retry, which is famous for sometimes taking actual days to deliver a message.
Doesn’t apply from 4G onwards, where everything is IP, but still.
Depending on what you mean by "needs a lot of signalling bandwidth" I think that is incorrect.
I recall the early SMS functionality being added to cellular phones after the introduction of 2G in the early 1990s and as I recall, one claim was it monetised the massive amount of spare signalling capacity on the network. In the UK I recall that being said in 1994 by Orange (the first UK 'challenger' network vs 1G incumbents CellNet and Vodafone) when I had a Nokia 2010 handset.
SMS or signaling cannot use the bandwidth used for voice, they are entirely separate. On 1G and 2G one SMS needs the same bandwidth as 8 calls to go through. The signaling line can run at insanely low bitrates (and there may be errors).
The main problem was too many phones in one place causing errors on the signaling line. Like a concert. You'd get to a point where maybe one call can go through every 10 seconds. Then one person tries to send an SMS "because he can't get through" ... and the phone helpfully keeps retrying to send the SMS, each retry causing >1 minute of nothing signaling on the network. The network is now dead and while existing calls work fine, you can't even hang up anymore, never mind making or receiving a call.
I wouldn't count on it. SMS is available on any cellphone. If you don't know what chat apps the other side has, it's still the trustworthy if clunky baseline.
For more than 10 years, SMS and a chat ap have lived side by side. The favorite chat app changed a few times, but SMS just plods along, never really gaining or losing market share.
>SMS just plods along, never really gaining or losing market share
SMS lost huge market share to messaging mobile apps so EU telecoms changed their business model from selling SMS messages and/or calls plans to selling GBs data plans. For example you can buy unlimited daily, weekly or monthly data plan or x amount of GBs data plan. Some EU telecoms went so far to sell bundled apps data plans like this https://upload.wikimedia.org/wikipedia/commons/4/4e/%2B_Smar...
Taken into account that mobile data is not always available it will take some time until SMS will be extinct. And this in a central european country who just upgraded phone numbers for fax machines.
To young people who never used SMS and will grow up only on WhatsApp, FB messenger, Viber, Snapchat etc.
Snapchat is basically MMS with rich user experience and advanced features. Is anybody still using MMS when you have something like WhatsApp and Snapchat?
SMS and MMS are still useful as communicating protocols and communication services when you don't have internet access but you can think of SMS as something like XMPP. Why would you use bare bone XMPP when you can use WhatsApp running on XMPP with 99 useful features that XMPP doesn't originally have and support.
Plenty of people don't care about sending images over messages with phones, they use email and facebook for that.
Plus in many pre-paid plans the amount of SMS is almost unlimited, or with packages like 5 000 per month, which hardly anyone ever consumes half of it.
Not just from a European POV, but also from Eastern-Asian and South-American POV. I don't know the rest of the world.
For me and my peers, SMS is for 2 factor auth, spammy advertising, and the occasional parent that mistakenly sends a SMS instead of a WhatsApp message.
Besides, almost everyone uses Whatsapp, regardless of the phone brand.