I understand why 4 snow tires instead of 2 but I don t have money to buy all 4 tires so should I just leave the all 4 all seasons on.?

Other answer:

Yes, leave the current all-season tires on the vehicle.

The general thought behind that is if you have 2 winter tires on the vehicle, driver's have a tendency to become accustomed to the grip the winter tires offer. This means they will drive faster, corner harder, brake later, etc. than the other all-season tires can handle which can result in a loss of control or even a collision.

If all 4 tires are the same, you always know what the limitation of those tires are and you ( hopefully ) drive accordingly.

Texas Underdog:
I thought that also, until I tried it. Put 2 winter tires on front of front wheel drive vehicle, and the first time I used the brakes going around a corner, the front ones held but the rear did not, and I spun the vehicle around in the middle of the road. My good luck was I wasn't going very fast, and nobody else was around me. Lesson learned, I went back (very carefully) the next day, and got 2 more for the rear axle. After that, all good.
I live in NE Ohio under the shadow of Lake Erie and lake effect snow storms. I haven't purchased a snow tire in over 30 years. I get around just fine on all season radials.
You want the same grip on all tires, not just the ones that power the vehicle, or you are likely to lose control. If you can't afford all 4, chains are less expensive but more labor intensive.
fito patrick:
Je veux tout simplement qui a invente le systeme de freinage?
A thought shared.
Gray Area:
That would be the safer option yes.
just buy two; if front wheel drive put on front if rear wheel drive put on back