But there are some areas of overlap. Consider Disguise Kit and Deception, for example.
Yeah... way back when while we were talking about Tools... the big issue was that some Tools were included that
duplicated things you already could do with specific skills. Thus those specific Tools were potentially pointless, especially when a player selected a Background that gave both the Tool proficiency *and* the applicable Skill proficiency, or the Class gave a duplicate proficiency.
So for example... the Athletics skill allows you to add your proficiency bonus to any STR checks you make to climb things. The Climber's Kit tool also allows you to add your proficiency bonus to any STR checks you make to climb things. So any Class and Background combination that granted you the Athletics skill *and* the Climber's Kit tool was a loss of something cool for that character. A Background might offer three useful tool proficiencies to do something cool... but if you already also have the applicable Skill, then you now only have two useful tool proficiencies.
Deception and the Disguise kit was another pair of overlapping things-- the Disguise kit allows you to add the proficiency bonus to your CHA checks to pass off pretending to be someone else... while the Deception *also* allows that. So any Class/Background combination that gave you both was a loss of one useful tool.
The only way Tools would be able to avoid this overlap and be a useful addition would be if there was not an applicable Skill that accomplished the same function. So for example... there was no Thievery skill in the playtest. However, there WAS Thieve's Tools. Which means the only way you could ever add your proficiency bonus to your DEX check to pick a lock or disable a trap was if you had proficiency in Thieve's Tool. THAT'S where the concept of the Tool was worthwhile. Because it gave a bonus to a certain check where no Skill ever applied.
So to fix this problem, the game has to do one of two things...
1) ONLY include Tools in the game for things to do that you
cannot do using a Skill. So the Climber's kit-- gone. Athletics grants you the ability to climb, and thus the tool is superfluous. The Healer's kit-- gone. Medicine grants you the ability to stabilize someone, and thus the tool is superfluous. The Disguise kit? Gone...
unless you were to change the Deception skill to only include verbal deceptions and lying. But any physical deceptions using disguises could only be accomplished (i.e. grant the proficiency bonus) using a Disguise kit. Thieve's Tools? Stays in. There's no Skill for opening locks or disabling traps, thus the Tool has a purpose. The Herbalism Kit? Stays in. There is no Skill that allows you to create potions of healing, thus the Tool has a purpose. Poisoner's Kit? Stays in. There is no Skill that allows you to create poisons, thus the Tool has a purpose.
or 2) Each Background grants 3 skills and 2 tool proficiencies... but there are more than 3 skill options and more than 2 tool options in their Background lists to choose from. That way you as a player can select options that avoid doubling up on duplicate functions of the skills and tools you get from your Background (and also Class.) After all... the Bounty Hunter background right now grants you ONLY a tool proficiency in Mounts (land)-- a Tool that 4 separate Classes also get-- the Barbarian, Fighter, Paladin, and Ranger. Which is 4 Classes for whom the Bounty Hunter is a less good choice since you now get NO worthwhile Tool proficiencies from that Background. So why would ever want to select it (other than strictly for story reasons?)
There is absolutely no reason why there should ever be any doubling up of duplicate abilities through the selection of Race, Background and Class. The game can easily be designed to avoid that. And we just have to hope that they realized that and accomplished it because otherwise it could be seen as a giant waste.