In some cultures, 'for sale' can imply desperation to sell, possibly leading to a lower price. The sign 'car for sale' often attracts bargain hunters.
Pro Tip 2/3
Immediate Availability
'For sale' suggests the item can be immediately acquired, unlike 'coming soon' listings. Everything in the store window was for sale and ready to take home.
Pro Tip 3/3
General Public
Items 'for sale' are usually available to anyone interested, not just specific people. The antique vase was for sale to the highest bidder.