Without some further and more specific clarification, it would be hard to answer this substantially. Medieval and early modern sumptuary laws differed widely across towns and states, or kingdoms, were used differently, for legions of reasons, were either secular or ecclesiastical, and so forth. So barring something more concrete, I can though answer some of the remarks presented.

There certainly were customs according to hierarchical positions and titles, though again, this varies greatly. For example, in Scottish sumptuary law:

1551 was a statute passed linking the number of dishes allowed to each social rank (earls not more than 8 dishes, lords 6, barons 4, burghers 3), with hospitality rules stipulating that the number of dishes should be determined by the rank of the chief guest (APS II: 488, c. 22).

The major statute of 1429 required that all men with an income above £20 a year should be well horsed and equipped 'as a gentleman ought to be'; some of these requirements were specific requiring a fur hat, 'dollblat habergone' [sleeveless armoured jacket] and the provision of stipulated weaponry ( Governance of the Consuming Passions A History of Sumptuary Law by Alan Hunt, p. 35 )

Perusing the literature on the subject, the argument and a case that it was done out of consideration for the poor, or anything akin to it, is quite non-existent.

The motivations were likewise complex, one can see various arguments based on hierarchy, supply, economic factors ( spending, protecting local interest and manufacturing, ... ) state or city income, ecclesiastical and moralizing critiques of luxury and extravagance which influenced secular sphere, and so forth.

We find this in one of the notable petitions in early middle ages, being significant in a sense that it was not done by a noble for personal reasons, but by craftsmen arguing on economic grounds for abolition of such laws in Milan;

... Now, moving on to the matter regarding the law. If one were to infer that freedom of dress should cause universal detriment to the city, we would reply that this might be true for those cities where the purchasing of clothes involves sending money to other regions, because it weakens and impoverishes cities in many respects. But this is not true in our city, in which all those products relating to clothing are made here with the greatest abundance, such that not only does money stay in the city but also we make even more money by trading with foreigners, so that the law, which would be much more beneficial to those other cities, would be exceedingly harmful in ours. And this is so because where the conditions differ so greatly, the laws should likewise differ. ... ( The right to dress sumptuary laws in a global perspective, c. 1200-1800 by Giorgio Riello )

But in same manner we have plenty of examples from medieval period of noblewomen petitioning, even to the Pope, to be exempt from laws, either individually or in groups. Notably:

Cristina Corner. She informed the pope that she possessed many fine clothes which she had been unable to wear since Giustiniani’s constitution. She begged His Holiness that she, Cristina Corner, born of noble blood, be allowed to wear the forbidden items for the honour of her parents, because of her great beauty, and also because such clothing had been customary in the city before this constitution was observed, For the payment of 4 ducats and 1 grosso to the papal treasury, Cristina was granted a licence to wear such items for three years. ( Sumptuary Law in Italy 1200-1500 by Catherine Kovesi )

I will gladly answer some follow-up of more specific nature, either for period, city, or state.