Even passenger aircraft are operated with compromises on 'safety' for reasons of economics. For example in my experience, every Captain of a passenger jet has a different opinions of such things how turbulent it has to be to order return to seat + seatbelts, and when you can and can't use cellphones in his plane. It's his call he's the one who's responsible.
Using a 100A MOSFET so you can get away with 5V Vgs at 1A Id (your example) is rarely economical.
Yeah the tone of my example was a bit extreme, but you've got to agree it's often more economical in the long run to use higher ID fets.
Here's an example from my experience. The circuit my Engineer 'designs' (more like lifted from somewhere) spec'd an IR IRFS4620PBF in it, which our buyer found OK this exact one £1.29 for 100 pcs, assuring me it has all the right suffixes in the part number, so it will work 'as designed'. His nicely-computer drawn circuit which impresses everyone he shows it to, I notice has now acquired extra power rails in it for his religious "10 V gate drive" and a fancy power sequencing system that 'protects' the FET should there be a failure in the any one of these extra supply rails he added, the design is beginning to look 'top heavy' this last week he's been working on it, so I'll take over and give him break (otherwise this project will run over budget). But that was after a 'guided realisation experience' with your truly as the Guide, trying my best not to damage his morale. (I'd rather he was slightly wrong and happy, than always right)
So I checked the datasheet myself and this IRFS4620PBF was Id(max)15A, and Rds(on)="78 milliohm". The VDS isn't much of an issue, because it's only 7.2 V we're dealing with.
OK, that's an old FET design, it happens to us all.
So I find these instead:
Fairchild FDB8441 100 pcs. £1.28 (a penny cheaper).
Id Cont:28A (double)
On State Resistance:0.0019ohm (can ditch the heatsink now)
Vgs th Typ:2.8V
I keep looking:
Fairchild FDB8447L 100 pcs.
£0.35
Id Cont:
50A
On State Resistance:0.0085ohm
Vgs th Typ:
1.9V (can ditch the top heavy paraphenalia too)
And see this too:
STM STP140NF75 100+ £1.14
Id Cont:
150A
On State Resistance:0.0075ohm
Vgs th Typ:4V
But to me it's not about the design, but the Designer.