What are the practical applications of do-end blocks?

the main use i have found for "do (code) end" is limiting or setting the function environment of certain variables, for example locally setting an already made variable to something else for use inside of a certain part of the code that changed part color or some type of property in a part, or you could use get and setfenv for more fun variable changing

besides that i never really found a use for it

Yes you are right, but uses for that can be different even tho i don't use them too, you can use them as a decoration like:

function()
    do -- configuration
        assert()
        assert()
        assert()
        assert()
        assert()
        assert()
        if not x then
            return
        end
    end

    -- and here the script goes
end)

Even tho you do not have to, also another use is for example having classes in one script and you would need to limit amount of variables so you do

do
    local class1 = {}

    function
    class1.test = true
end

do
    local class2 = {}

    function
    class1.test = true
end

print(class1) -- nil
print(class2) -- nil

And here you prevented uneccessary variables, overall it's mostly useless but i have found it a use once, for example i could split the code into modules but i needed one variable to be accessed from all the classes and defining it in every single module would be ehh so i used do for that:

local ImportantVariable = "WideSteal"

do
    local class1 = {}

    ImportantVariable.LoadClass(class1)
end

do
    local class2 = {}

    ImportantVariable.LoadClass(class2)
end

Instead of doing this in every single module

-- module 1
local ImportantVariable = "WideSteal"

-- module 2
local ImportantVariable = "WideSteal"

BUT here setfenv comes instead, if every single module will have function Init then you can get rid of do...end

-- script

local CustomEnviroment = {
    ImportantVariable = "WideSteal",
    print = print,
}

for module in pairs(modules) do
    module.init(CustomEnviroment)
end

-- module1

function module1.init(CustomEnviroment)
    setfenv(1, CustomEnviroment)
    print(ImportantVariable) --  WideSteal
end)

-- module2

function module1.init(CustomEnviroment)
    setfenv(1, CustomEnviroment)
    print(ImportantVariable) --  WideSteal
end)

so basically do...end has probably no uses except for decoration