Losing your inventory isn't that big of a deal, the game isn't a 3rd person shooter.
You're objectively wrong, have it backwards, and I will explain why. If the game were a shooter (first or third) it wouldn't be a big deal.
Doom, Quake, RTCW and many more classics in episodic structure all steal your inventory multiple times throughout the singleplayer. But it matters not. You chew through inventory fast, get to use all your arsenal constantly, and finding secrets is immediately rewarding. Ammo capacity limits are strict so you are constantly juggling weapons and using them all in satisfying frequency. Not Tomb Raider. TR is a slow-paced, exploration-heavy game with less than half the enemy count. Its secrets can take a lot of effort and time to discover, oftentimes hidden behind instant death traps that result in significant loss of progress if you fail, and furthermore the rewards can be miniscule in quantity (one shotgun box = 2 shells). Ammo is in short supply in TR, a lot of the time you are using weak-ass pistols, especially at the beginning, and the game encourages it further by many combat encounters vs melee enemies where attaining high ground and spamming infinite pistols on them is a dominant strategy (=no health or ammo lost). Enemies are also tanky, so when you do decide to go ham with the big guns, it is refreshing. The player's inventory has a lot of significance even though it is quite simple. A lot of time, skill and effort goes into building it up.
There is only one context in which it is "not a big deal", and that is if you the player do not play and think in a gameplay mindframe (e.g resource management, being skillful in combat encounters to come out on top of the game of attrition etc). Which you obviously don't.
You could misguidedly counter with "just use the resources then!", but first playthrough wherein you do not know this happens, that doesn't apply. Core Design turn up in their thug mobile, pull the rug from under you and mugs you of all your worth in typical English fashion.
Furthermore, there is always going to be some resource saving happening in the case of boss fights/tougher encounters. This shit straight undermines the game they created. They rob your guns in TR2 at the oil rig but not the rest of your inventory, that was the much smarter approach.