Clarisse describes a past of which Montag is unaware: A world with front porches, gardens, and rocking chairs.
What do these 3 items have in common? Why would Montag's society have ordered their removal?
They all encourage thinking. If people cannot participate in such activities, and are constantly stimulated, they will not have the ability to form their own thoughts (which is what Montag's repressive society wanted).
All three are made of wood, which is a scarce and very valuable resource in Montag's world. Wood is tightly regulated because there is so little to go around.
They don't have much in common, but they are all arbitrarily outlawed in Montag's society. No one knows why--the reasoning is unclear.
All three items are common in the suburbs, but not in urban apartments. Because Montag's society is mostly urban, there remains little need for such things.
These are Mildred's favorite things. Because the government watches Mildred closely, she is not allowed to own such materials.