There is no excuse for someone not having their own PC, tablet, smartphone or whatever.
The excuse for not carrying a smartphone is that not everybody has hundreds of dollars of discretionary income to spend on a data plan. Verizon and Sprint refuse entirely to activate voice-only service on a smartphone, and AT&T is known for cramming a data plan onto a voice-only SIM when the SIM is inserted into a smartphone. Should someone carry a laptop everywhere and risk having it stolen just in case he needs to access the Internet at someone's house? And even if so, would you let a house guest use your WLAN?
If they were my children, I'd have bought them each their own PC.
Would you also buy a laptop for one of your child's classmates who is on a play date at hour house but whose parents cannot afford to buy him his own laptop?