Any telescope or binocular used for astronomy is a scientific instrument and should be treated as such. Even the humblest one deserves care, since you'll be using it right at the limit of its capabilities trying to see faint objects or fine detail. In such critical work, little problems can make a big difference. Then again an observer's life is full of imperfections, and there's no point fretting about them. The right attitude toward optics means knowing when to be vigilant about care and when to relax.
Every optical instrument gets dirty.
Dirt on lenses or mirrors scatters light and reduces contrast. It makes dark skies less dark and bright objects less crisp. Keep the lens caps on when the instrument is not in use. If none are available, make your own, such as shower caps or cloth over the ends of a Newtonian reflector. I store my two reflectors positioned so both their main and secondary mirrors face slightly down.