Bestfresnel magnifying glass

I'm new to this topic so pardon me if it's a stupid question. but recently I watched a well-known youtuber give a great demo about starting fires in survival conditions using multiple methods. Then I saw someone post their fire kit here, and both times it never included a magnifying glass.

Fresnel magnifying glassfor reading

Is there some obvious reason I'm not aware of that these aren't part of every fire kit? Again, sorry in advance if it's a stupid question.

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there are plastic lenses and fresnel lenses (like a ribbon of thin plastic instead of a thick magnifier) that I think could be rugged and not shatter like glass