Question: Why Maple pdsolve still unable to solve 1D convection-diffusion pde?

Can one hope that next version of Maple will be able to solve the standard convection-diffusion pde in 1D?

pde:=diff(u(x,t),t)=d*diff(u(x,t),x$2)+c*diff(u(x,t),x);

in 1D. Even the most simple form with zero boundary conditions can't be solved.

pde:=diff(u(x,t),t)=d*diff(u(x,t),x$2)+c*diff(u(x,t),x);
bc:=u(0,t)=0,u(L,t)=0;
ic:=u(x,0)=f(x);
sol:=pdsolve([pde,ic,bc],u(x,t)) assuming d>0,c>0,L>0

              sol := NULL

I tried some HINT's also but not all of them.

FYI, Mathematica 12.1 is now able to solve the above PDE

ClearAll["Global`*"];
pde=D[u[x,t],t]==d*D[u[x,t],{x,2}]+c*D[u[x,t],x];
bc={u[0,t]==0,u[L,t]==0};
ic=u[x,0]==f[x];
DSolve[{pde,bc,ic},u[x,t],{x,t},Assumptions->{d>0,c>0,L>0}]

Gives

Is it possible I am overlooking some other option or a trick to obtain solution for the above using pdsolve? Only reason I am asking is that Maple can solve much more complicated PDE's and the above is one of the basic diffusion based PDE's. So I am surprised why Maple still can't solve this as it is just a seperation of variables method.

Maple 2020 on windows 10. Physics version 631