what was so special about the green wards

You could actually buy them instead of having to wait for your trinket to reload or visiting the fountain to load a sightstone.

When I started playing, there was also no limit to how many wards you could place or buy. (Then they set the buy three, place three limit).

Supports used to literally be warding bitches, and Riot wants to encourage the entire team to ward, hence the limits and not being able to buy them outright.

they are more affordable then and are harder to destroy in the sense the enemy cant walk into the brush and kill it off without having some detection

The only thing I miss is being able to have 10+ of them when I leave base, and gaining vision of a full quarter of the jungle before an objective fight. Sure it took two inventory slots for 10 wards, but back then I didn't really have anything else to buy as a support.