That's for 10C temperature rise - which is severe. I monitor my PCBs with a thermal camera and would worry if a trace was getting hotter than the chips!
The main reasons for wide traces for supply and ground is not that the traces get too hot, its:
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There is too much IR voltage drop across the trace (for instance the 5.0V rail could become 4.8V with too much resistance) - the fact this resistance is only heating the trace by 10C is not the point, its the voltage loss and increased impedance of the supply seen by the load that may matter.
For ground connections this is even more important as analog signals are typically measured relative to ground and its assumed to be the same ground everywhere. -
There is too much stray inductance for thin traces, preventing the decoupling capacitors doing an effective job.
I'd suggest much much wider than 0.25mm, perhaps 1.5mm, if there's space.
And another point some chips rely on power and ground traces for some heatsinking, meaning wide traces are assumed.