The majority of end user devices are run from within private networks protected from the Internet. If you have connected to your cell provider, then in the majority the cell providers are running their own private networks. For one reason the IPv4 address space is limited as such, that there are no other possibilities. IPv4 is still the important protocol compared to IPv6. Second, it is that those providers, want to protect you. Some don't even allow cross communication.
If you devices are connected with Wifi, then there is the very same situation. There is almost no campus, commercial, and home network, that gives you public route-able IP addresses. I only know a view deployments were you get public route-able IP addresses at conferences like C3, EMF, and alike.
tl/dr: No, the end user devices is not easily to reach without additional infrastructure.
The majority of end user devices are run from within private networks protected from the Internet. If you have connected to your cell provider, then in the majority the cell providers are running their own private networks. For one reason the IPv4 address space is limited as such, that there are no other possibilities. IPv4 is still the important protocol compared to IPv6. Second, it is that those providers, want to protect you. Some don't even allow cross communication.
If you devices are connected with Wifi, then there is the very same situation. There is almost no campus, commercial, and home network, that gives you public route-able IP addresses. I only know a view deployments were you get public route-able IP addresses at conferences like C3, EMF, and alike.
tl/dr: No, the end user devices is not easily to reach without additional infrastructure.