
for anime titles: it's just because those series are the biggest. "mew mew" in particular is only 2 seasons and wasn't the most popular, so it's just a coincidence that you've seen it so much. "precure" on the other hand is HUGE, a over 20 season magical girl anime that is still on-going today, which is why you see it alot.
as for character names: it's similar to why superheroes have 'man' at the end of their name. superman, batman, spiderman, etc. these characters have real names (peter parker is spiderman, for example) but their hero names all share a similar pattern to make it recognizable that 'oh, this is a superhero character' even if you know nothing about them. it's similar with magical girls. cure dream's real name is nozomi, the 'cure' part is just to highlight that 'hey, this is a precure character!!'