Why don't dicarboxylic acids show hydrogen bonding in spite of the fact that carboxylic acids exist usually as dimers in polar aprotic solvent?
I would like to object the statement dicarboxylic acids would not engage hydrogen bonding.  Terephthalic acids ($\ce{HO2C-C6H4-CO2H}$) are a prominent example since early attempts to formalize the description of intra- and intermolecular hydrogen bonding in the solid state. Consider the pairing of benzoïc acid and $p$-terephthalic acid, sharing the same motif of hydrogen donors and acceptors, described as $R_2^2(8)$ in Etter's notation:

(Etter, Acc. Chem. Res. 1990, 23, 120-126,  doi 10.1021/ar00172a005)
But there is no limit to $p$-substitution to find this motif again, e.g.:

(Holy et al., Collect. Czech. Chem. Commun. 2006, 71, 139-154, doi 10.1135/cccc20060139, researchgate.net)