Tank crews do not have eyes in the back of their heads. They have some MASSIVE blind spots, especially when buttoned up. Therefore, with a bit of patience and some small amount of skill, it's not that hard to sneak up close enough to use improvised AT weapons against them.
Yes, it takes balls, but it can be done.
This is why tanks should NEVER operate in close country without infantry support.
https://youtu.be/V7fZ4wxWP1Q
And older tanks are much more vulnerable to improvised weapons than newer one. Isn't that one of the reasons tank design is always being improved? Taking a 50+ year old AFV onto a modern battlefield is just begging for destruction.