I went to a convention once, deciding that it was redundant to bring my laptop with me when my smartphone alone should have been perfectly capable to do all of my online only Internet tasks.

I ended up having my credit card skimmed from an ATM, and someone withdrew around $500-1000 as a result of that, which was about half of the money that I had on my account, and allocated towards that particular trip.

Let me tell you, it was not comforting, sitting on a hotel bed with a tiny overheating smartphone (Galaxy S2 back then), navigating the bank's website with my thumbs, on a slow mobile connection, which kept on crashing. Their phone lines were busy for 3+ hours because it was a major event.

I realized in that particular moment, that I always needed a backup, high speed computer (or laptop) with a full physical keyboard and mouse for specifically those circumstances, where time was absolutely critical.