Yes. Marvel and DC (and most other) put them out - trade paperbacks, chronological collections, omnibus collections, single (or double) issue reprints - all the damn time.
There are, but the collections are mostly paperbacks (the hardcovers are generally VERY expensive omnibuses, some of which can cost hundreds of dollars, or short runs/specific stories). Marvel’s Essentials line is black and white reprints of ~3 years worth of a title per volume. There are about 22 Essentials volumes of the various Spider-Man titles which had run up to the mid-80s. If you want colour, you’ll be forking out more for the Masterworks editions. (DC’s equivalent lines are Showcase Presents and Archive Editions.)
Of course, with characters who’ve been around for 50-80 years (as most of the big superheroes have), you don’t necessarily want to try to read them all, in order…because there’s so very much of it, and the timbre changes between the Golden Age, the interregnum, the Silver Age, the Bronze Age, and the modern age (and even within them).
As to the multiple titles, there’s several reasons that happens.
The most common is that the really big characters - Superman, Batman, Spider-Man, the X-Men - will usually carry more than one title at a time (not always with their names in the title - Superman always headlines Action Comics, even when it’s an anthology, and Detective has been a Batman solo for decades) - usually 2 or 3, but Superman, Batman, and Spider-Man have all gotten to 4, and Batman currently has 5 (though one’s a limited series, and another’s ending soon). In cases where the extra titles aren’t in alternate universes (like the Ultimate line, Marvel Adventures, one of DC’s cartoon-based comic books, etc), the books are usually more or less independent, but sometimes they’re tightly plotted, essentially becoming a single title that happened to come out multiple times a month. When the latter is the case, collections will follow the storyline, not the originating title, and the individual issues will be marked with the reading order. (Usually.)
Sometimes the companies change the title of an ongoing series for various reasons, such as a change in direction, adding a secondary star, the backmatter taking over, etc. (Marvel has done this more than DC.)
Sometimes a title is cancelled, then immediately restarted, sometimes with a new title, to get a new #1 issue. (USUALLY this is a good jumping on point, but it’s not always a reboot of the character.)
Sometimes it’s a case of a new character with the same name (as was the case with The Superior Spider-Man), but usually, that’ll just involve a renumbering, rather than a new sub-/super-title.
) and enjoyed them.