What’s even the point of skill proficiencies? You can accomplish the same thing with a tool proficiency, so is there even a point?
All (non-armor) proficiencies in D&D 5e do the exact same thing– they let you add your proficiency bonus to some sort of roll. Skill and tool proficiencies, in particular, both let you add your proficiency bonus to certain ability checks. For skills, that’s anything involving the use of that skill. For tools, that’s anything involving the use of those tools.
Because proficiencies in 5e don’t stack– you either add your proficiency modifier or you don’t– having overlapping tool and skill proficiencies is bad. For example, there’s practically no benefit to having proficiency with disguise kits and the deception skill– you can leverage your skill at pulling off disguises pretty much every time you can tell a lie and vice versa.
So, then, broader skills and tools are, obviously, better than specific ones. Tools aren’t inherently more or less broad than skills, though. They are just different.
Skills, in the most default RAW context, are tied to specific abilities by being subsets of them. That means Perception proficiency will only ever apply to Wisdom checks in such a context.
Tools, on the other hand, are not tied to any one ability score. Instead, they are tied to the involvement of the tools or parts of the tools in the task. That means that Thieves’ Tools proficiency, while typically applied to Dex checks, could also apply to e.g. an Intelligence check to analyze how a defeated construct worked, provided the tools were used to disassemble it as part of the check.
Tools, then, are better when you have several different ability scores involved in what is essentially a single task or family of tasks and want to add your proficiency bonus to all of them, while skills are better when you want to ensure that a single attribute will be exclusively used for a particular kind of activity.