A telescope spends almost all its life indoors and takes its damage in the few minutes at either end of a session. Cases and covers are cheap insurance against exactly those minutes, and against the slower damage of storage.
What actually damages a telescope
Being knocked over, being carried by the wrong part, and dew drying on optics and leaving deposits. Optical surfaces are far more robust than owners fear and coatings are more delicate than they look, so the rule is to protect against impact and moisture and to clean as rarely as possible.
Hard cases against soft
A hard case protects against impact and costs more; a padded soft case is lighter and adequate for a tube that travels in a car boot with nothing on top of it. For eyepieces, a small hard case with foam cut-outs is the right answer, because small expensive things get lost and dropped.
Covers, dust and the open tube
A newtonian's open tube is the one that collects dust, and a fitted cover or even a shower cap over the top ring is enough. Dust on a mirror matters far less than people expect: a visibly dusty mirror loses a fraction of a per cent of light, and cleaning it badly can cost far more.
Storing at the right temperature
A telescope stored in a warm house needs half an hour or more to cool to outdoor temperature before it performs, and a large one longer. Storing it in an unheated garage or shed removes that wait entirely, which for a spontaneous observer is worth more than any accessory.
Questions people ask about telescope
Do I need a case for my telescope?
For transport, yes, and a padded soft case is usually enough. For eyepieces, a foam lined case is worth it immediately.
How should I store a telescope?
Covered, dry and ideally at outdoor temperature, so it is ready to use rather than needing to cool down first.
Should I clean my telescope mirror?
Rarely. Dust costs almost no light, and careless cleaning damages coatings. Clean only when there is a visible film, and follow the maker's method.