Overparameterized constructors

[Deduction42]

Normally, if I type in something like

Normal{Float32}(0,1) 

based on the default behaviour of constructors, I would expect a response similar to

Normal{Float32}(μ=0.0f0, σ=1.0f0)

where the parameters get converted to the appropriate type. However, instead, I get the following error:

ERROR: MethodError: no method matching Normal{Float32}(::Float64, ::Float64)

When looking at the source code, I see that the default constructor is overwritten:

struct Normal{T<:Real} <: ContinuousUnivariateDistribution
    μ::T
    σ::T
    Normal{T}(µ::T, σ::T) where {T<:Real} = new{T}(µ, σ)
end

Is there any reason why the default constructor is so specific that the input values MUST be the same type as the constructor's parameter?